Been messing around with the theme changer. See it on http://euans.net/blog/
Doesn't work yet - it will change when you push the "use permanently" link, but not just from the select box. This is a problem in lib-common.php (which always uses the saved value from $_CONF) but I haven't been able to fix it yet. I also stripped the browser check and haven't put it back yet, but if someone can work out the lib-common stuff that would be good.
Unless someone has already made one of these.
-- Heather Engineering
-- No job too small