I like to run multiple browsers. Firefox as a development and default browser. Chrome or Safari for web surfing, and SeaMonkey for those multiple profile sort of situations.
Chrome Firefox Safari SeaMonkey
Cygwin - Want a Bash shell on Windows? Want some of your favorite Unix utilities? Then Cygwin is for you.
Java - Must have the JDK.Notepad++ - It is always a good idea to have a good native programming text editor around. For those times when you need a quick tweak or just want to view something. For Windows, Notepad++ is the best option out there.
NetBeans - A great Java open source IDE.
SQLite - File based SQL database.
Subversion - Windows 7 64 bit command line version.
Filezilla - A secure FTP client for Windows. When transferring files with a Unix system, FTP or SFTP is still your best choice.
Pidgin - Best open source chat client for Windows.
Putty - Windows SSH and Telnet clientThunderbird - Mozilla's awesome e-mail client.
Open Office - Open source office suite.
Paint.net - Open source graphics program
SVG Anti-Virus - Great free or paid anti-virus you can buy and install online.