We use ip.board from Invision and I think it looks good, we have a subsection for the forum and our main site is seperate but the membership information is combined.Look at http://punetworks.com/ and http://punetworks.com/pulounge if you want to see how we did it, its a site about cars.
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They do have mobile specific css which works pretty good, I've looked at our site punetworks.com/pulounge and it looks nice.
We use ip.board from Invision and I think it looks good, we have a subsection for the forum and our main site is seperate but the membership information is combined.Look at http://punetworks.com/ and http://punetworks.com/pulounge if you want to see how we did it, its a site about cars.