Some of the stuff I've written which might be useful/interesting to a wider audience.
(There's plenty of stuff which wouldn't be, trust me!)
This one I didn't write, but it appears to have been abandoned by the original author. Since I use it in one of my other projects I picked it up, updated the dependencies and stuff, then figured I might as well publish the result so other people can get some use out of it as well.
If you want to add CAPTCHA support to (for example) your contact forms, but you don't want to invite Google to insert it's tentacles into your website, then the captchas.net server is worth a look. It's free if you don't mind their branding, or you can pay to remove it.