No but I could build you one

Criss Myers

I can build you basic web browser app
That can't download

Criss Myers

i've setup kiosk environments before with just safari and mcx.

there are also plugin and built-in options for firefox and chrome. i just tried chrome's kiosk mode on os x, and it didn't work, though.

There are a few ways to do this. Router/Network level, like a squid proxy, smooth wall, etc. The other is client based. I have used this in the past for some clients back in the day

http://www1.k9webprotection.com/

-Tom

Note: That if you already use a proxy on site, then K9 will break your internet browsing for the client you installed it on

K9 only works directly going out through the internet, not if there is a proxy sitting on your network.