I've been looking at Wt (pronounced Witty), via Heartless on #php, for the last 30 minutes or so. I've got to say, I'm pretty impressed.
The name and concept seems inspired from Qt, or perhaps WxWidgets, and is quite robust. Hardly pretty at this stage and I've not yet hacked anything together, but quite cool. Especially if you insist on using C++ to develop your websites.
Edit: Paul / Chip has a very good point on using Wt;
Given my frustrations in the past, in dealing with ultimatums from designers (despite implementing templated systems), I can fully understand Chip's point… Things never look as good as they initially do. Arses.
On the plus side, Chip appears to be throwing his hand into a web toolkit of his own. It'll be interesting to see what he throws together.