I second the WD40. It's practically harmless to your paint. Also GooGone works VERY well at removing most adhesives. For the s***ty dealer sticker on my trunk, I saturated it with GooGone, and then used the edge of my driver's license to gently scrape the vinyl letters off. It also worked for the Peace dove emblem that was on the bumper (previous owner.) That thing was on there TIGHT with the 3M foam adhesive tape. It took 3-4 applications of GooGone to really cut through the adhesive, but it worked.
NOTE: Do NOT use Goof Off in lieu of GooGone. Goof Off is lacquer thinner, GooGone is citrus oil.