A Fortune 500 customer of Zepheira's has a problem that could readily be solved with SKOS. You might think that would be sufficient to attract the attention of some tools vendors, especially since SKOS is in "last call" at the W3C and is likely to become a standard later this year. If that is so, I've missed it.
Can anyone tell me where to get decent tool support for SKOS?
Mulgara has some cool support for SKOS, as I mentioned here. Unfortunately, the state of that support still requires some care and feeding by an expert.
I approached Revelytix, hoping that they would agree to provide SKOS support in Knoodl, but they demurred until at least later this year. It should be easy for them given their existing support for OWL and their use of Mulgara.
Another alternative may be ThManager, an Open Source SKOS editor/visualizer.
Until tools vendors support SKOS directly, we are limited to existing taxonomy creation and maintenance tools, such as BiblioTech or Synaptica to build ANSI/NISO standard thesauri (Z39.19) then convert them to SKOS. For the moment, though, conversion tools seem to be in the same boat as editors.