Best anti spam methods

[eluser]Christophe28[/eluser]
Hello,

I created a 'register' page using codeigniter. I have used a captcha (plugin), but now I'm not sure this is good enough.

Sometimes I see anti-spam methods like '9 + 1 = '. Does this work? Seems like a pretty easy thing to find for the spambots?

Can somebody suggest the best anti spam methods?

Christophe