Anidandesign.com has released a pretty cool shape set for Photoshop. These shapes will allow you to create RSS icons with shapes that can be enlarged or shrunken while still maintaining high quality. If you are unsure as to what a Photoshop shape is, be sure to read the About.com shape guide which explains the difference between brushes and shapes while also explaining how to install them.
P.S. My favorite shape is the light bulb, what is yours?