I've done a quick-and-dirty implementation of Bram's stochastic trust metric, which works on the Advogato graph. It seems to give plausible results, and on the Advogato graph (4000 active nodes, 40000 arcs) it takes 6 seconds to do 1000 iterations (which gives results to a precision of about 1.6%, where 100% is maximum trust). It's a combination of Perl and C.
To test it, you'll need the Advogato trust graph. Thanks to gary for pointing out that this is available as a graphviz .dot file here:
This is the form that my current implementation expects the trust graph to be in. There's a simple test command line in the Makefile.
Update - just got email from Brad saying that this isn't the metric as he originally meant to describe it. Caveat downloader.