Heckler Magazine - Detailed free ramp plans including funbox, pyramid, launch and various pipes. - http://www.heckler.com/ramps/index.php
Halfpipe Pictures - Includes photos of the steps taken in building his son's halfpipe. Also includes free plans and FAQs. - http://www.rickdahlen.com/pipepix/halfpipe.html
Ramp Plans Dot Org - A compliation of plans from all over the web with attrition, photos, FAQs, glossary, and related links. Also provides a message board with several topics. - http://rampplans.org/
Skatepark Guide - Resource for designing and building concrete skate parks and portable ramp kit parks. Skate park guide book and CD ROM available. - http://www.skateparkguide.com/