Classic video game fans, rejoice! GameTap.com, the website where you can play hundreds of old-school video games for a $10 monthly fee, will start offering a handful of games for free, starting next month. The catch? You must sit through a video commercial first, and there will be an ad on the side of the screen during gameplay. Sounds easy enough, and the free titles are a great bunch, including Space Invaders, Rampage, Metal Slug, Joust (woo hoo!) and a Tomb Raider game. Just wish the site offered Berzerk, which we’d so pay for…