Tunnels & Trolls is a fantasy roleplaying game (FRP), created by Ken St. Andre. Its name was deliberately chosen to be evocative of Dungeons & Dragons. (Later homages were paid by the hyper-realistic Chivalry & Sorcery and the disturbingly popular Bunnies & Burrows). Ken liked the concept of FRP, but wanted to create a game with a simpler set of rules. And that only used six sided dice. Lots and lots and lots of six sided dice.
T&T has a more whimsical feel than D&D. Ken says his goal was a world based on The Lord of The Rings as it would have been done by Marvel Comics in 1974 with Conan, Elric, the Gray Mouser and a host of badguys thrown in. For example, some of the most frequently used spells are Hidey Hole, Oh There It Is, and the ever-popular Take That You Fiend!.
After selling out his first run of 100 copies, Ken was approached by Rick Loomis, owner-manager of Flying Buffalo. Liz Danforth illustrated and edited the second edition. One of the early draws of the T&T ruleset was the availability of solo dungeons. Rick Loomis wrote the first, Buffalo Castle, although I feel Deathtrap Equalizer, has a way cooler name. Over the next two decades, Mike Stackpole and others at Flying Buffalo have made edits and modifications to ruleset, complicating it somewhat.
Ken adapted the ruleset to write the first reverse D&D game, called Monsters! Monsters!, where you play a hapless monster beset by marauding player characters. It was edited by Steve Jackson and published by Metagaming in 1976
There was a computer adaption done in the mid 1990s, but the general opinion on rec.games.frp.* and from the author is that it sucks. Bigtime. Use the floppies for frisbees.
Liz Danforth later went on to do the artwork for Steve Jackson's The Fantasy Trip, cards for Magic: The Gathering, and a full time career as a fantasy artist. Mike Stackpole did a lot of work for Battletech and is a published author. Ken is happily married and still working as a librarian in Phoenix, NM. According to his web site, he has plans to distribute a sixth edition ruleset electronically.
http://www.geocities.com/Area51/Cavern/9921/ (Ken's official site)
http://www.flyingbuffalo.com/tandt.htm (publisher's site)