Even better than WD-40 for dissolving adhesive residue is one of the cleansers/degreasers based on citrus oil. OrangeGlo is probably the best known brand, but there are lots of others. The stuff cuts through almost anything sticky or greasy, and its citrus smell a great improvement over the oily banana smell of WD-40. Wear nitrile gloves when you use it though, because it will also strip the oil off your skin, and if you must spray it, be very careful to not let any of the mist get on you, especially in your eyes.
Nonstick cooking spray (Pam, etc.) is also pretty good for dissolving adhesives because of the lecithin it contains.
