Are you swapping out the crystals and overclocking them?
If not, strapping it to a larger heatsink is more than sufficient for passive cooling.
I'd love to try and overclock it, I've found a few guides online, the first is the most comprehensive.
http://wtfmoogle.com/?p=3334http://www.designer2k2.at/mods/elektronik/85-block-erupter-overclocking.htmlIt looks semi, indepth but something I could manage. Though I don't have all the tools. I could get the electrical components at Radio Shack I bet though.
But I decided on the cooling first (less destructive) before I get into the OC'ing. I've always liked TEC's but never had one, just wanted to play with it.