Honestly, I've always been fond of Urban Arana, which is pretty much "D&D in the modern day." Cars can get magic paintjobs that let them travel along electrical lines, wizards e-mail their enemies .hex files to curse their hard drive, civic construction projects sometimes dig into ancient forgotten dungeons, and all sorts of other fun stuff. I think I've got the book somewhere on my hard drive if you want.

Alternatively, X-Crawl gives the same sort of "modern fantasy" thing while including dungeon crawling as an extreme sport, giving the players a chance to get corporate sponsorships and travel around the world.