Just ran across this really cool double wall heat exchanger from Butler Sun Solutions.
This is not your normal heat exchanger though, it is made to be installed in an existing water heater. Here is the description from their site:
1. Solar Heat Exchange Wand (Patent Pending)
The Butler Sun Solutions Solar Wand allows readily available, standard hot water tanks to be adapted quickly and easily for solar heating. The Solar Wand is a double walled heat exchanger that fits into any full size, 40 ga....
Do It Yourself Solar
