Last year I built a off road buggy using the Haynes Manual "build your own off-road buggy for £100 or less". This video breifly explains how i do it, the finnished buggy is great fun and if you have acces to the tools needed (welder, grinder......) I would definatly recomend it.
The book can be purchased from  http://www.amazon.co.uk/Build-Your-Own-Off-road-Buggy/dp/1859606423/ref=sr_1_1?s=books&ie=UTF8&qid=1329677413&sr=1-1 or if you are in the USA http://www.amazon.com/Build-Your-Off-Road-Buggy-little/dp/1859606423/ref=sr_1_1?ie=UTF8&qid=1329757360&sr=8-1

Specifications

Engine:  Electric start 110cc motorbike engine
Gears: 4 (no reverse)
Suspention: Front and seat
Seat: Racing kart seat with suspension
Steering: Colomn from robin reliant, stock tie rods for acerman steering
Frame: 1.5" steel tube


Hope this is useful.