Nothing tangible, like job offers. I have a couple of sites and each has a blog for my two main areas of interest: tech topics and mechanical stuff. Whenever I struggle to figure something out or compile information to make a decision, I write a blog post about it. This has proven useful several times when I needed to do something, vaguely remembered having done something similar before, and quickly find the details on my own site. Judging by a few comments, it's helped a few others over the years, too.

I also keep wikis on those sites for more interconnected information.