If you need a really nice, large set of free icons to use in your web or desktop applications, I recommend the Fugue set. As of November 30, 2009, it has 2360 icons, includes the Adobe Photoshop PSD files in case you need to modify them and they are free if you provide a link back to the site from your application, or you can pay a fee of $50 and skip the link back.
Below is a sample of the icons:
David is an IT professional with over 26 years of experience (he started his career as a teenager). He has programmed in more languages and on more types of computers (and similar devices) than he can remember, including TRS-80 Model I Level 2, Commodore Vic-20, C-64 and C-128, Industrial Process Controllers, CP/M machines, and Intel 80x86+ architectures. He currently uses Microsoft .NET Framework tools and SQL Server.
When he's not geeking out, he studies the Martial Art, Aikido; engages in community volunteer work; writes fiction (as well as non-fiction blogs); and does home rennovation work.
He lives in Charlotte NC, USA. 
