Pretty URL is a Simple Machine Forum Mod that re-writes the URL structure of your SMF forum and make it more Search Engine friendly.
Example
All these point to the same topic

Default SMF URLs: http:// www.cyvin.com/index.php?topic=2969.0

Search Engine Friendly URLs: http:// www.cyvin.com/index.php/topic,2969.0.html

Pretty URLs: http://www.cyvin.com/offtopic/unleaded-gas/

Pretty URL is of great SE0 benefits to SMF forums.

Click Here to Download Pretty URL