I have several differnt forums on differnt hosts and my favorite for
reliablity and speed is proboards, in fact my largest forum is hosted by proboards. I also have a new forum that is a myBB forum hosted by
createmyBB, I am really impressed with this host so far too.
I tried several forum hosts but I hate the ads so freeforums.org was my final choice and despite the "failure" back in July I decided to stick with them. Their support service is great!
Have your heard about Forumotion?
It's very easy to sign up, you simply need to provide the forum name, subdomain (what will appear in the URL), password, email address and the category of the forum. All of this takes around two minutes, after which you can choose the initial forum skin, then you are taken directly to your new forum.
I'm not sure if you mean the type you set up yourself or the type you just sign up at a site like InvisionFree or Proboards, etc? But whichever, it would bne PHPBB and ProBoards, def... though I use proboards for everything nowadays cause I have the whole skinning and well, everything down to a T.