Anti-virus:Microsoft Security Essentials
- Free AV. Nice and light on resources.
ProgrammingMicrosoft Visual Studio 2010 Express
- Actually includes C#, C++, Visual Basic, a WebDev package (Most ASP.NET) and SQL Server Express 2012. Free for non-commercial use (Apart from SQL server, that one's free for commercial use).XNA Game Studio 4.0
- a bunch of game-centric libraries for use with C#. Can be used to make games for Windows, 360 and WinPhone.Git
- Nice free version control system. Can be used in conjunction with bitbucket
which provides free Git repositories.
Other useful things:LastPass
- Password locker.WordPress
- Website/Blog tool. Supported by a large portion of web hosts.OpenSSH
- Network client, used for secure tunelling.
I'll add more as I think of them.