Inmeria.net analyzed over 7000 websites between Dec07 and Jan.08 and came up with a great vendor market share report:
It is interesting to see the different market share of the top vendors. Omniture, now with HBX, is certainly leading the high-end vendor pack.
Still the top 5 vendors don't give much of an overview.
There are more than 200 web analytics vendors our there. What would interest me is how many websites run Sitemeter, Statcounter vs. Google Analytics (and Gatineau).
Most of these free solutions are widely spread, but always fall under the radar