Is there an option available to make new registrants type in the funky letters - to screen spambots? I forget the name of that approach, but I couldn't find anything under spambot in search.
Captcha will be a part of SMF 1.1 RC3.
Its CAPTCHA image verification if you want it now for SMF 1.0.7 or SMF 1.1 RC2
http://mods.simplemachines.org/index.php?mod=277