Installing seo4smf mod:

1. copy the file from http://custom.simplemachines.org/mods/index.php?mod=518
2. install the mod into the site (admin > main > packages)
3. rename the file to .htaccess
4. enable “Search engine friendly URLs” from your admin area (Features and Settings)
5. enable the mod (admin > configuration > Seo4SMF Admin, check Seo4SMF Enable, Remove board from front of topic, Beautifying url for profile members)

seo2smf mod, forums discussions:
http://www.webmasterstalks.com/seo-4-smf-b46.0/
http://www.simplemachines.org/community/index.php?topic=155313.20

Patch to fix the displaying of links inside the pages:
http://www.webmasterstalks.com/seo-4-smf/seo-4-smf-link-problem-t1489.0.html