I've been toying with Akismet and ReCAPTCHA a bit, and I feel comfortable adding comments to this blog again. I last tried this this almost four years ago, and the near-instant flood of Texas Hold 'Em spam made me turn them off. ReCAPTCHA uses the Internet Archive's book-scanning project as a source of difficult-to-read text, so there's a social good that results from any submitted comments.
I had originally wanted to use Akismet as a primary filter, so that the ReCAPTCHA form was only displayed if a comment triggered their spam alarm. However, I became uncomfortable with the comments on my personal site being used to stock a commercial database. I will still use this pattern elsewhere, because it's a self-evidently better user experience, but while you are in my house you shall be forced to suffer.
Comments only work on relatively recent posts - anything older than three months or so has the form turned off.