I read a few years back that tyre manufacturers reckon your average road tyre has about 80% of the grip it does in the dry.
Dunno if I'd fancy testing that theory, though! :shock:
I move around a lot more on the bike when it's wet. This keeps the bike more upright in the turns so you get more grip. Also the best thing you can do is RELAX and keep breathing! Wet riding is almost like meditating to me, and I have to say i quite enjoy it and having to be that much more smooth with everything.
And don't get fooled into buying super-sticky treadless track tyres, because they will catch you out in the rain, and the chances are you won't be able to ride anywhere near the limits of even a modern sports touring tyre even on a dry track.