A missing feature of Pyblosxom was the 'extended entry' capability that several other blogging systems have. Continuing in my experiment with Pyblosxom, a second plugin for Pyblosxom, which comes in at a whopping 32 lines of code (a sign of a decent architecture!).
The markup is relatively simple, and seems to be compatible with the various entry parsers (textile, ReST, etc.):
Entry title ((( This is the summary ))) This is the full entry.