A friend of mine built a track in his backyard he used drain tubeing like dirtburners ask when they do a rebuild and they will likely give you any of the tube they replace which is not perfect but still very usable. You will also want a hard rake, hand tamper, shovels, wheel barrle, push broom, tiller(you might be able to rent one) and alot of hard work but once done they are alot of fun:) orion make a lap counter they sell for around $60 on ebay and are worth it if you want to get some race times.

here is a pic of their track

http://i79.photobucket.com/albums/j131/cmain88z/backyardtrack2.jpg