I've been doing a little research on W3C validation, but I'm not sure to what extent validation helps rank. I mean, not even Google passes validation.

I ran my own test and didn't see enough improvement in the page I validated to prove causal relationship. But one thing I did find was that aside from the challenge the corrections provide, and simply knowing that your page is 'perfect' in the eyes of W3C, I was able to increase my code-to-content ratio, further focus my page content, and make better use of keywords in ways that I (embarrassingly enough) had quite wrong. So some real good came out of it. But did I see any advantage gained over my non-validated competitors?

Unfortunately, no I did not.

And this seems to be the general consensus just about everywhere I searched. If anyone has found materials that discuss otherwise (markedly so), I'd really like to check it out.

Another thing: The info available through the W3C validation site is some great stuff, especially what I found on validating flash.

All the best,
The Lion.