In one site I'm getting a lot of spam via a contact form created with Freeform. Is there a good solution, besides adding a CAPTCHA?
The other advantage to Akismet is you don't need user-unfriendly CAPTCHAs. Even honeypots can be outsmarted by bots on occasion, and they're not effective against human spammers.
The one caveat with Low NoSpam on Freeform is that you can't moderate flagged submissions from the CP. Though that hasn't really been a problem for me.
I like Sean's suggestions, but if you are avoiding CAPTCHA simply because they can be difficult to enter in for a user, check out Accessible CAPTCHA to see if it will suit your needs. You can set up a series of questions that will be picked at random instead, that a user has to answer.
I've used it on sites and have had some fun having the questions be "on brand" for the site.
In addition to CAPTCHA, you might want to take a look at VZ Bad Behavior - it will block known spammers from the entire site. Give it a look; I've used it and had great success with it.
Not sure of any other ways of preventing forms to be submitted without a captcha, Sean's idea sounds great though and definitely worth looking into. But you can always go with RECAPTCHA if you really need to use a CAPTCHA. I hate them (as most people probably do) but here's the link:
It's ADA compliant, your visitors help translate books and its probably the most popular. Snaptcha would do the trick as well, but I personally think that if you need a captcha (which I hate :)) then go with RECAPTCHA :)
Oh and it's completely FREE too!!
I released a (free) anti-spam addon for Freeform which a) adds a honeypot field and b) checks the submission's IP address against a few blacklists. You might want to give it a try - I've used it to mostly eliminate spam submissions on several sites.
I've also created a plugin for Mollom. You can find it here. https://github.com/tsmith86/EE_mollom I do need to update it though.
I've had good results with Freeform Anti-Spam. It places honeypot fields and can filter results for those that do get through. I've been able to remove the hated captcha field from some client forms using this. http://devot-ee.com/add-ons/freeform-anti-spam
There is also the free Honeypot for ExpressionEngine add-on which works with Solspace Freeform, Solspace User and Expresso/DevDemon FreeMember.
Have you seen the new version of ReCaptcha? It's about as unobtrusive as you get, it's a tick box that monitors for human style movements and clicks, really nice IMHO.
I always use this : https://devot-ee.com/add-ons/recaptcha
It's kind of like a drop in replacement for the build in Captcha so it works anywhere the built in one does, including Freeform front and back end. You can use your existing captcha settings via EE CP and I beleive it has tags to easily include in many forms!
Best of all it's free! This module with the new style of ReCaptcha makes for a winning combo in my book, and not messing about at all!