Here's a list of the best free Vbulletin SEO mods out there. I'm using these on my VB forums and most of them are small plugins or template edits. I have no experience with VBseo because i think it's way overpriced but hey, that's my opinion. You can get great results with the following list of SEO mods:
- External Link Titles - Retrieves descriptive titles for external posted links. Allows for better link recognition and, in theory, could help increase page SEO.
- Hide Last Post Date For Guests - This mod simply hides last post date for guests, It hides last post dates in main page and in each forum page. Dates are hidden only for guests.
Also - some people say that it is good for Google. - Link Canonicalization - Sets a Canonical URL to prevent duplicate content.
- Next/Previous Thread Title Replacement - Replace the "Next Thread" and "Previous Thread" links with thread titles.
- vBSEO :: Sitemap Generator - Generate a Google & Yahoo Sitemap for your Forums. This is a must have mod actually
- Remove duplicate content due to &order=desc in forumdisplay pages urls - 1- prevent duplicate content detected in Google webmaster tools.
2- gives single url for each forumdisplay page
3- SEO value : remove Duplicate urls for search engines to determine one url to index
4- higher page rank you might get for right internal linking
5- Internal linking now goes along urls in sitemap generated by vbseo sitemap generator - Description for meta and bookmarksite on showthread - Instead of showing a short meta description on showthread pages, this will show the thread preview text instead. Works better Check the source on Streetcars - Turbochargers and take a look at the meta description to see it in action.
- Signature only on first post - What's the use if your users have links in their sigs and showing those same links over and over again? This will show it only once per user per page.
There's also something you can do with the <if condition="$bbuserinfo[userid]"> conditional. If you don't allow guests to post, use this conditional to remove reply, newthread and quote buttons for guests and search engines too. For example, find in the postbit_legacy (or postbit if you don't use legacy): <if condition="$post['replylink']"> and replace it with <if condition="$post['replylink'] AND $bbuserinfo[userid]"> . Guest won't see the quote button anymore.
That's it for now. Will update this when i think of some more stuff i did or when i find some 
