Open Source alternatives to proprietary Enterprise software

This list is a collaborative effort to build the ultimate list of enterprise software and their Open Source and SaaS alternatives. feel free to comment and propose names since this is quite an ambitious target. If you like the list, feel free to digg it.
Title Open Source alternative(s) Saas alternative(s)
AutoCAD 2009
BRL-CAD
Archimedes
QCAD Community Edition
 Floorplanner.com
BlueKiwi
Drupal
Elgg
PeopleAggregator
 Google Sites
BMC IT Service Support for the Midsized Business (formerly Magic)
RT - Request Tracker
OTRS - Open source Ticket Request System
 ZenDesk
BMC Remedy for IT Service Providers
OTRS - Open source Ticket Request System
RT - Request Tracker
 ZenDesk
BMC Remedy IT Service Management
OTRS - Open source Ticket Request System
RT - Request Tracker
 ZenDesk
Bonjour Avahi
Business Object Data Integrator
Kettle
Talend Open Studio
Apatar
 LucidEra
Clearspace
MindTouch Core
Drupal
 Google Sites
Confluence
xWiki
Drupal
MindTouch Core
 Google Sites
CubeCart
OSCommerce
Magento
ZenCart
DieselPoint Search
Apache Lucene
Carrot2
Xapian
Apache Solr
 Pay-As-You-Go SearchBlox
Documentum
Alfresco
Nuxeo 5
 SpringCM
Endeca Information Access Platform
Apache Lucene
Pentaho
Exalead CloudView
Apache Lucene
Carrot2
Apache Solr
 Pay-As-You-Go SearchBlox
FAST Enterprise Search Platform
Apache Lucene
Carrot2
Google Search Appliance (GSA) Apache Lucene
HEAT Product Suite
OTRS - Open source Ticket Request System
RT - Request Tracker
IBM WebSphere Portal
Liferay
JBoss Portal
 Google Sites
IDOL Server Apache Lucene
Internet Explorer
Google Chrome
Firefox
JIRA
Mantis
Bugzilla
Livelink ECM
Alfresco
Nuxeo 5
Microsoft Dynamics CRM
Sugar Open Source
OpenCRX
Microsoft Project
Open Workbench
OpenProj
 Campfire
Microsoft Search Server 2008
Apache Lucene
Apache Solr
LucidWorks for Solr
MQSeries
ActiveMQ
JbossMQ
Norton Ghost Clonezilla
OmniFind Enterprise Edition Apache Lucene
Opera
Firefox
Google Chrome
Konqueror
Flock
Oracle 10g
MySQL 5.x Community Edition
PostgreSQL
Oracle 11g
MySQL 5.x Community Edition
PostgreSQL
Oracle Weblogic Application Server
Jboss Application Server
Tomcat
Geronimo
WebSphere AS Community Edition
Oracle WebLogic Portal
Liferay
eXo Platform
Drupal
 Google Sites
PHPizabi
Drupal
Elgg
PeopleAggregator
Powercenter
Talend Open Studio
Kettle
Apatar
 LucidEra
Safari
Google Chrome
Firefox
SearchBlox
Apache Lucene
Carrot2
Sharepoint 2007
JBoss Portal
Drupal
Alfresco
SiteCatalyst
awstats
Piwik
 Google Analytics
Top Braid Composer Protégé
Track-It
Mantis
Bugzilla
Trident
Gecko
Webkit
KHTML
Unica
awstats
Piwik
Xiti
Google Analytics
Woopra
Velocity Search Platform
Apache Lucene
Carrot2
WebTrends
awstats
Piwik
Xiti
Google Analytics
Woopra
Title Proprietary alternative(s) Saas alternative(s)
ICEpdf
4Store Virtuoso Universal Server
4Suite Server
Acceleo
ActiveMQ MQSeries
Adeona
Alfresco
Filenet
Documentum
Sharepoint 2007
Xythos Enterprise Document Management Suite
SpringCM
Apache Ant
Apache AXIS
Apache Batik
Apache Cocoon
Apache Directory Server
Apache Directory Studio
Apache FOP
Apache Hadoop
Apache Harmony
Apache HTTP Server Internet Information Server -IIS-
Apache Jackrabbit
Apache Jakarta JMeter
Apache Jakarta POI
Apache Lucene
Velocity Search Platform
Exalead CloudView
 Pay-As-You-Go SearchBlox
Apache Maven
Apache Module mod_proxy_balancer
Apache MyFaces
Apache ODE
Apache OFBiz
Apache Regexp
Apache Shale
Apache Solr
Velocity Search Platform
Exalead CloudView
Apache SpamAssassin
Apache Synapse
Apache Turbine
Apache Xerces C++ XML Parser
Apache Xerces Java XML Parser
Apache Xerces Perl XML Parser
Apache Xindice
Apatar
Business Object Data Integrator
Powercenter
 LucidEra
Appcelerator Titanium
Aras Innovator
Asterisk
awstats SiteCatalyst Google Analytics
b2evolution
BIRT
BlazeDS
Blueprint
Bonita
Boxee
BRL-CAD AutoCAD 2009
Bugzilla JIRA
Cappuccino
Carrot2
Exalead CloudView
Velocity Search Platform
Cassandra
Celtix
CentOS
Clojure
Clonezilla Norton Ghost
CMS Made Simple
Codendi
Concrete5
CVS
cyn.in Open Source Community Edition
BlueKiwi
Clearspace
db4o
Derby
Dimdim Open Source
Django
Dojo Toolkit
Dolphin Smart Community Builder
DotClear
dotProject
Drools
Druid
Drupal
Sharepoint 2007
Oracle WebLogic Portal
IBM WebSphere Portal
Drupal Webform module
DWR Isomorphic
EasyBeans
eGroupware
Ekiga
Elgg
Enhydra Octopus
Business Object Data Integrator
Powercenter
 LucidEra
Enomalism
eTicket
EUCALYPTUS
Eventum JIRA ZenDesk
eXo Platform
Ext GWT
extJS Enterprise Ajax framework
eZ Publish 3
Fedora Directory Server
Firefox
Opera
Internet Explorer
Safari
Flax IDOL Server
Flex 3
Flock
Internet Explorer
Safari
Opera
Foswiki Confluence
Freeway CubeCart
Frog CMS
Funambol
Gallery
GATE
GateIn
JBoss Portal
eXo Platform
Gecko
Presto
Trident
Git
Glassfish
Websphere Application Server
Oracle Weblogic Application Server
GLPI
GNU Dialer
Google Chrome
Opera
Internet Explorer
Google Wave Sharepoint 2007
Grails
GroundWork Monitor Open Source
GWT - Google Web Toolkit -
HAProxy
Heartbeat
Hibernate
Hippo CMS
Hive
Hudson
Hyperic
ICEfaces
ImpressCMS
Interchange
JaikuEngine
JasperReports
Java System Application Server
jBilling
Jboss Application Server
Websphere Application Server
Oracle Weblogic Application Server
JBoss Portal
IBM WebSphere Portal
Oracle WebLogic Portal
CA's CleverPath Portal
Sharepoint 2007
JBossESB
jBPM
Jersey
Jitterbit
JOnAS
Websphere Application Server
Oracle Weblogic Application Server
Joram
jQuery
JSPWiki Confluence
Kettle
Business Object Data Integrator
Powercenter
 LucidEra
KHTML Presto
KnowledgeTree Document Management System
KPlato Microsoft Project
Launchpad
LemonLdap
Liberum Help Desk JIRA
Liferay
Vignette Application Portal
Oracle WebLogic Portal
IBM WebSphere Portal
Lift
LightTPD Internet Information Server -IIS-
LimeSurvey
Linux Virtual Server
Log4J
Lomboz
LuceneWorks
LucidGaze for Solr
LucidWorks for Solr
Maarch
Magento
Mantis JIRA
MaxDB (formaly SAP DB)
MediaWiki Confluence
Mercurial
Metasploit
MG4J
MiaCMS
MindTouch Core Confluence
MODx
MongoDB
moo.fx
Moodle
mootools
Movable Type
MySQL 5.x Community Edition
MythTV Windows Media Center
Nagios
nmap
Nuxeo 5
Filenet
Documentum
Sharepoint 2007
Livelink ECM
SpringCM
Xythos Enterprise Document Management Suite
Open Web Server Internet Information Server -IIS-
Openbravo
Openbravo POS
OpenClinica
OpenCMS
OpenDS
OpenERP
Openmeetings
OpenMRS
OpenNMS
OpenOffice.org
OpenPipeline
Velocity Search Platform
IDOL Server
FAST Enterprise Search Platform
OpenPipeline
Velocity Search Platform
FAST Enterprise Search Platform
 Pay-As-You-Go SearchBlox
OpenProj Microsoft Project
Campfire
@Task
OpenVPN
OpenX
Orbeon Forms
OS Ticket
OSCommerce
osCSS
OTRS - Open source Ticket Request System JIRA ZenDesk
OXID eShop Community Edition
Oxite
PeopleAggregator
PeTALS
PHPList
PHPMyAdmin
PHPWiki Confluence
Pidgin
Pig
Piwik SiteCatalyst
Google Analytics
Xiti
Woopra
Play!
POSH
PostgreSQL
Oracle 10g
Oracle 11g
PrestaShop
ProcessMaker RunMyProcess
Project.net Microsoft Project
Protégé
Prototype
Prototype
QCAD Community Edition AutoCAD 2009
Quotero
Filenet
Livelink ECM
Documentum
SpringCM
Xythos Enterprise Document Management Suite
R
Radiant CMS
Red Hat Enterprise Server
Red5
Redmine
Rsync
RT - Request Tracker JIRA ZenDesk
Samba
Scalix Server Community Edition
script.aculo.us
ServiceMix
Simplexo
Velocity Search Platform
IDOL Server
 Pay-As-You-Go SearchBlox
Spago
SpagoBI
Sphinx
Microsoft Search Server 2008
Exalead CloudView
Velocity Search Platform
 Pay-As-You-Go SearchBlox
SPIP
StarUML
Status.net Twitter
Struts
Sugar Open Source Microsoft Dynamics CRM
SVK
Synergy
Talend Open Profiler
Talend Open Studio
Business Object Data Integrator
Powercenter
 LucidEra
Telligent Community Server
TightVNC
Tomcat
TopCased
Tornado Twitter
Trac JIRA
TWiki
Typo3
Ubercart
Useme
VICIDIAL dialer CallFire.com
Virtuoso Open Source Edition Virtuoso Universal Server
VMukti
Webkit
WengoPhone
Wicket
WordPress
Wordpress MU
WP e-Commerce
WSO2 ESB
Xapian
IDOL Server
Velocity Search Platform
 Pay-As-You-Go SearchBlox
XBMC
XCart
XMind
xTuple PostBooks Edition
xWiki Confluence
ZenCart
Zenoss
Zimplit
Title Proprietary alternative(s) Open Source alternative(s)
5pm
@Task Microsoft Project
Project.net
ProjectPier
Alenty SiteCatalyst awstats
CallFire.com
GNU Dialer
VICIDIAL dialer
Campfire
Central Desktop
Comapping FreeMind
Cordys jBPM
DeskAway
DimDim
Openmeetings
Dimdim Open Source
ETSEM CaaS
Evernote
Floorplanner.com AutoCAD 2009
FormAssembly
LimeSurvey
JSurvey
Google Analytics SiteCatalyst
awstats
Piwik
Google Apps
Google Docs
Google Notebook
Google Sites
GoToMeeting
Dimdim Open Source
Openmeetings
IndexTools
SiteCatalyst
WebTrends
 awstats
IsoTracker
Kaltura
LimeService
phpESP
JSurvey
LimeSurvey
LotusLive Engage
LucidEra
Business Object Data Integrator
Powercenter
Talend Open Studio
Apatar
Kettle
Enhydra Octopus
MindMeister
Nedstat SiteCatalyst awstats
OpenSource Contract Manager
Pay-As-You-Go SearchBlox
Microsoft Search Server 2008
Velocity Search Platform
Exalead CloudView
Apache Lucene
DieselPoint Search
ProjectOffice.net
Quantcast SiteCatalyst
Piwik
awstats
RunMyProcess
Intalio|BPMS Community Edition
Apache ODE
jBPM
Salesforce CRM
SpringCM
Filenet
Documentum
Livelink ECM
Alfresco
Nuxeo 5
SuccessFactors
Ta-da List
TimeBridge
Twitter
Status.net
Tornado
Vyew
Openmeetings
Dimdim Open Source
WebEx
Dimdim Open Source
Openmeetings
Woopra
Woozweb
Wordpress
Workday Financial Management™
Workday Human Capital Management™
Workday Payroll™
Wrike
Writeboard
Xiti SiteCatalyst
awstats
Piwik
Xythos Enterprise Document Management Suite
Documentum
Filenet
Livelink ECM
Alfresco
Nuxeo 5
Yugma Dimdim Open Source
ZenDesk
JIRA
BMC IT Service Support for the Midsized Business (formerly Magic)
Bugzilla
Mantis