Most convention centers (and some airports) run a wireless network that
is un-secured. No WEP or anything like that.

But when you try to browse to a web site, they have some router that
intercepts your http traffic and you get diverted to some company that
puts up a web page telling you that if you want internet access you have
to pay something like $10 an hour, $50 per day, etc.

Is there any way to hack around that kind of setup?

Maybe they only monitor port-80? Maybe VPN will work?

Any ideas?

Is there a name for this kind of internet access?