I suggest you sign up with Icon Buffet. They have a great selection of Icons and lllustrations for purchase, but better than that if you sign up you get monthly icon sets to use as you like (besides reselling).
Here’s a peek at the quality. Use em for Desktop Apps or Web or whatever else you can think of.
Now I’m just looking for an application idea where I can use some these great icons. Also once your signed up you can trade the free sets with other users so let me know if you need Durango Research or Oslo Atmosphere, since I’ve got em.