Oxiclean and hot water. Labels fall off in under an hour. Just wipe off the excess glue while rinsing and all is well.
Sam Adams, Dogfish Head, Great Lakes all come off real easy. I try to stick with Sams from my local beer distributor. They let me pick and choose from the return pile and just pay the 5 cents return per bottle. Just gotta find the ones without the green stuff growing inside!
Make sure to rinse your own bottles as soon as you pour, that way they stay clean for the next use.