If you use WordPress like me with the majority of sites, you may have a similar problem that I do. On 3 of my popular WordPress sites, I get nailed by more then a handful of spam accounts getting created each day. For this blog, it got to the point where I actually had to stop accepting user registrations.
Last week I read that ThemeHybrid released Registration Honeypot which was supposed to trick spambots from creating new spam accounts. I tried it on one site and was amazed. No new spam accounts. I have now since added it to my two other sites and new spam user accounts were stopped as well. In short, this plugin creates a hidden input field that only spambots can see.
A great plugin and really simple idea. I hope the developer continues to develop this plugin because I can see spambots finding a way around this in the near future. Until then, my inbox is quite empty of new user accounts.
Download Registration Honeypot here -> http://themehybrid.com/plugins/registration-honeypot