Here's a forum game I spotted on the Terry Pratchett Books forum:
Pick a book, and change one of the words to something completely different, "with, as the ancient scrolls say, hilarious results". (- Jingo)
Then post it here.
- Champignons of Mystara - 1,000 cooking recipes with unripe white Portobello mushrooms, and how to find them in Brun, Skothar and Davania.
- Friend Folio - a hefty grimoire detailing magic rituals that will assist lonely spellcasters in social networking.
- Unearthed Gymkhana - the noble history of competitive Gnomish badger-riding.
If you prefer, you can pick any suitably geeky book you'd like, not necessarily just roleplaying books.