Host a forum on your IP? Dunno what you're talking about. There is, though: www.invisionfree.com www.phpbbforfree.com
no dont use invisionfree as they put ads and you will never get members. Best way is to get a domain. Go to http://www.freewebspace.net/forum find free hosting in the free hosting section. Come back to me and I will install a forum for you.
IF is the best I am at a site of theres right now trying to get a prize its pretty tyte and nice site as well