I wrote a paper called A Fast Parallel Branch and Bound Algorithm for Treewidth, in ICTAI 2011. It can compute treewidth in multi-core. I used lots of heuristics and spent lots of time refining the program.
I was a random undergraduate student in China and didn't make it to a good conference. But based on my experiment results, I think my program is very fast. I solved many unsolved benchmarks in Treewidth lib, and my program was 40 times faster than a algorithm proposed by Zhou and Hansen in IJCAI 09..
I'm not working on this topic any more. But if my previous work is helpful, you can download my program (src and exe) from http://www.callowbird.com/undergraduate-stuff.html, and have a try. (still, it is very very slow on a slightly larger instance)