I've just spent most of my evening at the task of scrubbing labels off of wine bottles and I remember someone asking what the best way to go about it was.
Heat. You can soak them for days in cold water and it won't be as effective as a minute or so in hot water. Depending on the type of glue, a lot of labels will peal off with no effort at all. Others you might have to fight with but the hotter you keep the water the easier they will be.
That being said, there are some types of glue that, no matter how hot the water is, will stay behind and gum up after you have struggled to scrub off the label. These ones are hardly worth the trouble, but if you've got this far with them, you'll probably need some kind of solvent to get the glue off. A little bit of lighter fluid works well.
Heat. You can soak them for days in cold water and it won't be as effective as a minute or so in hot water. Depending on the type of glue, a lot of labels will peal off with no effort at all. Others you might have to fight with but the hotter you keep the water the easier they will be.
That being said, there are some types of glue that, no matter how hot the water is, will stay behind and gum up after you have struggled to scrub off the label. These ones are hardly worth the trouble, but if you've got this far with them, you'll probably need some kind of solvent to get the glue off. A little bit of lighter fluid works well.