gprime said:What do you mean don't support? You should easily be able to install the requisite files on any normal host.
That said, I know many people who recommend Site5 for forum hosting.
Amnezia said:you can install it on any host that has php and mysql (including host gator). The host it self will not support 3rd party applications but it doesnt mean they wont work. I think you'd be hard pressed to find a host that actually did offer support for vanilla. You can get support from the vanilla forums.

