InvisionFree.com redirects to zIFBoards.com so I think it's under new ownership, but old InvisionFree forums should still be up. I miss those boards...
I still see Invisionfree forums around today! Just mainly for RP sites, but they're not bad to start your first forum (or five ) with. Better to go free than pay for something that could flop.
While I wasn't around when it was popular, I have used Invisionfree and it's pretty good. However if I was to set up a forum that ran on IPB 1.3, I'd go with Jcink over Invisionfree since there are many features on Jcink that are not on zIFboards. Man I wish I was around when Invisionfree was the best site to set your forum up at... I didn't get a computer until 2006-2007 and even then I didn't have access to the internet until I got my laptop in 2008. :V