Can't afford a BOB trailer, or an Xtracycle? I happened across this, and thought it would get Clancy's juices flowing in particular.
It's a website with DIY bicycle trailers - made out of plywood, bamboo, conduit, etc. (Click HERE.)
My favorite is the expandable "Bike Camper" built by a "25 year old Chicago youth." Looks to be out of an old Popular Mechanics or something. It also looks eerily like a coffin to me... dunno if I could get comfortable in it, especially with the lids closed during "adverse weather"!
(Most of the trailers look more practical than the camper... it just caught my attention in particular.)