Thanks for clearing that up Rand, I'll stick to the one subdomain.

These links are the one's that got me thinking.

http://www.mattcutts.com/blog/subdomains-and-subdirectories/

http://www.webmasterworld.com/google/4339166.htm

Also, I was under the impression that sub forums on one domain were viewed as different sites in the SERPs but try searching for 'bodybuilding'.  You'll see www.bodybuilding.com at the top and a list of pages from that site and 2 further subdirectories are included (forum.bodybuilding.com and bodyspace.bodybuilding.com).

Although a personal preference only, I prefer subdomains and think forum.domain.com and blog.domain.com look much better than domain.com/forum and I would do it this way IF the rankings were unaffected.

I've had a good read on this one and just wondered whether the info on the below link is still valid 3 years on:

http://www.seomoz.org/blog/understanding-root-domains-subdomains-vs-subfolders-microsites

My main site is a forum but I want to add further content in the form of a blog.  It seems logical to me that domain.com/blog/ would make more sense than blog.domain.com as the the content and inbound links to the blog would also help the forum where it's on the same subdomain, however I just wanted to make sure that was still the case as I've also read that Google now see a subdomain and subfolder in the same way if set up correctly in webmaster tools and this solution would look neater if that was the case.

Thanks all.

These links are the one's that got me thinking.

http://www.mattcutts.com/blog/subdomains-and-subdirectories/

http://www.webmasterworld.com/google/4339166.htm

Also, I was under the impression that sub forums on one domain were viewed as different sites in the SERPs but try searching for 'bodybuilding'.  You'll see www.bodybuilding.com at the top and a list of pages from that site and 2 further subdirectories are included (forum.bodybuilding.com and bodyspace.bodybuilding.com).

Although a personal preference only, I prefer subdomains and think forum.domain.com and blog.domain.com look much better than domain.com/forum and I would do it this way IF the rankings were unaffected.