[john_flintstone]

A forum I run in Ireland doesn't have a need for Captchas. The forum is very regional and niche - no genuine foreign visitors - so we blocked every country apart from Ireland and the UK from posting comments. Result - no spam.

This wouldn't work for many forums, but if it's local, you really don't need to open it to the world.

[icebraining]

So, if I was an Irish guy travelling (or even an emigrant), I'd be blocked? That seems unfortunate.

On my forum I just added a question about Portuguese history. Anyone who understands the languages can find the answer in a couple of minutes, but bots really aren't that clever.

[aapl]

I frequent a couple of niche forums where the rule is that you have to write an introductory post of at least X sentences (or come up with original witty answers to a list of questions etc.) before you are allowed to post anything else. All introductions are read by admins or volunteers and approved if as long as they seem written by a human. No spammers and very few trolls.

[josscrowcroft]

Wow - such a nice and simple approach, bet this would work for many similar small forums..

[tripzilch]

Similarly, if you run the forum on a LAN instead of the Internet, you also don't get any spam! :-/

[Fando]

that's great