You really need to check out Scott Hanselman's 2005 Ultimate Developer and Power Users Tool List: http://www.hanselman.com/blog/ScottHanselmans2005UltimateDeveloperAndPowerUsersToolList.aspx
I'm not saying you will use everything Scott suggests, but I've already done several installs and I'm not done yet. I knew about FireFox and BgInfo, but forgot to bring them along to my latest machine. NotePad2 was new to me, but immediately became my default text editor. As I get through more of the FireFox extensions, I'll sing out if anything grabs me by the lapels.
Bill J