you could try one of these, fits to any bike, preferably 26inch wheels.
I use it for day to day stuff, hauling and shopping etc. The most I have carried on it is around 200lbs + me and even carried a 42in TV for a friend from a local electrical store. The face of the sales guy when I took it out and strapped it to the bike was priceless
It makes a great tourer and it gets a lot of use as a platform for my large format photography habit around the local are.
http://garibeet.wordpress.com/
http://www.xtracycle.com/
Forgot to mention I also have a trailer for if I really want to haul.
Cheers
Gari