Well, I spent Easter Sunday building this trailer.
It started as two pieces of 1/2"emt (electrical conduit, $1.80ea @ Lowe's), an old wheelchair discovered in a pile of junk behind someone's house (I paid them $20, probably could have been free), a piece of uni-strut from a garbage can outside WSECU in downtown Olympia, an air-hose coupling from Harbor Freight (already had this but not more than $2 new) and the bin was ~$12 on sale @ one of the big Lowe's-Depot stores. There is a little bit of aluminum angle stock from my scrap bin and a bit of scrap hose for the flexible bit of the hitch.
Some creative bending-
a hacksaw and dremel-
Plus a little barely adequate welding (read: ugly) yields a surprisingly strong trailer. I weigh about 215lbs and it didn't even budge under my weight. I toted home my full weeks groceries in it without a problem. It tracks great, and with the large wheels has no problem going over curbs. I kept the C.O.B. low and it seems to be happy with that. It seems very light, I haven't weighed it yet, but I can lift it easily (my guess is about 30lbs). I found some plans online for another trailer using bike wheels. I will be making one of those soon. This is fun.
I am one step closer to bike commuting for everything. The kids make it hard with their band instruments, but other than that, I hope to be bike only by summer quarter.