These two threads on Anandtech are frequently updated with sales on XBox/GameCube games and accessories. Thought some of you folks might be interested in giving 'em a peek as well: XBox GameCube
Does Target really have XBOX games that cheap? The closest Target to me is about 30 miles but I would pick up some of those $15 and $20 games and make it worth the drive.
It depends on the location. My local Target has some of those deals, but their XBox section is laughably small. From what I understand, they're marking down older inventory to make room for new games, but if they've already managed to clear out enough titles or if they didn't order those older titles in the first place...
It might be worth calling and asking to make sure. For extra verification, ask them to scan the title to get the price as the actual price tags have a tendency to be rather out of date.