Choose Your Own Adventure
I was wondering whether there’s still a market for Choose Your Own Adventure™ books, so I dug up some links. The Choose Your Own Adventure website bears no obvious connection to the books; it’s closer in spirit to Blog Your Own Adventure. Google Answers says the trademark is registered but dead, and recommends hiring a lawyer if you need to know what that means.
Wikipedia has a list of titles from the original series and an informative article on the genre of interactive fiction (IF).
Update
The domain choose-your-own-adventure.com is now unclaimed (as is chooseyourownadventure.com); also Blog Your Own Adventure seems to be broken.
The Wikipedia article on gamebooks is more relevant than the one linked above.