This is my fourth week at my new job, and this link was the first one I've found that was blocked my the corporate firewall (didn't even realize we had such a policy) - the reason? Pornography. Man, I'm missing out.
that said:
DungeonDelveXL is a fully-featured Role Playing Game (RPG), written entirely inside Microsoft Excel. It features a large, procedurally generated world and dungeons, with enormous potential to explore endlessly varying missions with your party of brave adventurers. And all inside a spreadsheet.