Sean tipped me off about mailbucket, it's a way to turn a mailing list into an RSS feed for people who lurk on high-volume mailing lists. After I posted on the Bazaar mailing list about this, Aaron told me that Gmane had a very similar feature. I've used the Gmane web interface to mailing lists before, but had not seen the RSS feature.
Now I've tried both, and for plain-text emails so prevalent on software development mailing lists, the formatting that comes through in mailbucket is much nicer than Gmane RSS. Of course, if I want to give someone a link to an old mail thread, Gmane is the obvious choice.