I like the citrus degreaser suggestion. Will have to try that.
However, the method I've used so far which is VERY effective is to use lighter fluid. Yeah, I know - not the nicest stuff. Just do in a well ventilated area and recommend to wear rubber gloves. First soak labels in warm water for half hour, peel off the paper, then squirt some lighter fluid on paper towel or a rag (or directly on glue/bottle). Glue wipes right off.