There are powdercoaters doing industrial type work in nearly all large cities - its that popular. If you're not picky about color, and use a powder they're using for another job at the time, they'll coat a bike frame for low cost - 30-40 bucks. Be sure to plug any holes you don't want coated (or else you'll have to clean them out later).
Chemical paint remover works to some extent, depending on paint. It totally removed paint from a cannondale (except for decal area). Barely touched the paint on an older trek. Sanding is a real PITA - not too bad on main triangle, but stays, bb, brake bosses and dropouts take forever. A dremel with sanding wheel will go a lot faster (be super careful on aluminum). Sand (or bead) blasting is the way to go if the price is right. BTW most powdercoat shops are setup to sand blast as part of prep work.
As a few folks have already stated, rattle can paint jobs are very disappointing - lot a work, kinda crappy results. I found a textured paint to spray with - it's a flat finish with textured surface. The good thing about it is when i nick this paint at some point down the road, I can touch it up with an artist's brush and you can't even see the repair. Plus, the texture hides the little paint job defects you would see if you used a more common glossy rattle can paint. Obviously I'm not concerned with getting professional looking results - nothing fancy, just protecting the steel.
http://www.rustoleum.com/CBGProduct.asp?pid=27
PS - If rattle-can spraying an aluminum frame, you need a good primer. It's hard to get paint to stick to aluminum, even when you've prepped the surface well. Paint flakes off aluminum. It's painful to watch. Usually start's flaking off 10 minutes into bike reassembly. Steel works better with rattle can paint jobs.