The current TeamCity version is 5.1.3, it can be downloaded form the download page.
The latest TeamCity version in 4.5.x branch is 4.5.6, download page.
Below is a list of previous TeamCity releases.
TeamCity 5.1.2
Build: 13430
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.1.1
Build: 13398
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.1
Build: 13360
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.0.3
Build: 10821
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.0.2
Build: 10784
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.0.1
Build: 10715
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 5.0
Build: 10669
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.6
Build: 9140
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.5
Build: 9103
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.4
Build: 9071
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.3
Build: 9035
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.2
Build: 9029
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5.1
Build: 8975
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.5
Build: 8944
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.0.2
Build: 8222
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.0.1
Build: 8171
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)
TeamCity 4.0
Build: 8080
Windows installer
Archive with bundled Tomcat (any platform)
Java EE container (war)