MyBB Community Forums

I am in need of a plugin that can change the urls of links on my site to what I want.

Example: Instead of http://example.com/forums/index.php it would be http://example.com/forums/index
http://example.com/forums/showthread.php?tid=9000 --> http://example.com/forums/thread?tid=9000
and so on....

That's not really something that's easy to do with a plugin. Something like Google SEO may be more along the lines of what you are looking for. You could do your own URL rewrites, but that can be a pain as it involves a lot of regex.

Have you looked into the google SEO plugin? Last I had checked it was a little buggy, but a lot of administrators have found it to work well for their forums, and of course I self host my website on a weird server configuration.