I looked at WordHoard today, a tool spearheaded by Martin Mueller of NWU, one of the grandmasters in the TEI text-encoding initiative (he was also behind the MONK project).
I was struck by some of the cool aspects of WordHoard, such as the stemming and POS infrastructure and the Bean scripting window, as well as some of the weirdness (MySQL-backed hibernate objects that require full rebuild for every XML edit?).
Some of the linguistic services available from MONK are incorporated in the MorphAdorner that is still available on BitBucket (with cool online examples hosted at NWU). There is also a collaboration with the Lucene-based BlackLab index.
The TEI community seems to be big fans of the Oxygen XML editor, but I can handle a lot of pain for 240US$, to be quite honest about it.
I also noticed that the next TEI conference is in Vienna, in September, and that they have a call for papers out now. Maybe I can think of something cool to write on.