Can registered users EASILY upload images to my site?

Hello

I have an image based website (contestedart.com) and I have to manually upload all of my users images. This includes photoshoping them to the appropriate sizes (Small thumbnail and large expanded size) and then uploading as usual. It is very time consuming when I get a surge of submissions. Is there a way for my users to easily upload an image themselves and have it automatically resize and post itself? I am tired of spending all of my time posting the artwork…any suggestions would be GREATLY appreciated.

-Chris