I've been trialing the free version of FoolBotHoneyPot before I purchase the full version, but it's still allowing spam bots to register, apparently detecting them as humans... It doesn't fill me with much confidence to pay for the full version as our site runs on a tight budget.
I installed the free version of CustomImageCaptcha, but again it's still allowing bots to register.
I used Q&A with site specific questions before hand - only questions a human could get right, but this is still failing.
Completely at a loss.