(Ref: http://yoast.com)

While preparing my previous post on new features in WordPress 2.9, I ran across a ticket in Trac for something I'd been wanting to do for a while: specify a subfolder of the uploads directory for specific plugins, like my Blog Icons plugin, to upload their files to. This way, the blog icons plugin would upload its files to /uploads/blog-icons/, which is a lot better for everyone.