Use Oxyclean. Some lables will come right off and others will take a little work. Make sure to use hot water. Most glue will still be on there is you only soke for a couple of hours so just rub it off with you hand, very very easy. Then Rinse in hot water.
used oxyclean in hotwater let soak 30 min. label and most of glue came right off. What ever glue was left just went around the bottle with a sponge. quick rinse put em on the dryer nice and clean. worked great and no harder than washing dishes by hand. Although some were harder than other to get off. But even with that said it was really easy just let those ones soak a tab bit longer
I recently used PBW (professional brewers wash, I believe) from a LHBS. It was about 2.99 for a bag. two tablespoons has removed labels from about 70 bottles and it is still going. quick rinse with hot water and then no-rinse sanitizer and the bottles are ready to go.