Want a great service to offer your site users? I love this idea from Gigablast. According to them, "you can create your own topic specific search engine in minutes. Gigablast's revolutionary, new technology allows you to create a list of up to 200 web sites (or subsites) and a search box that searches just those sites. Give your visitors a unique search experience, completely free of charge. For instance, if you have a site about horses, why not create a horse-specific search engine?" To create your own topic specific search engine, follow the directions given at www.gigablast.com/byose.html
This not only gives your users some useful content, but it can be used in other ways as well. What if you own 5 sites that are all industry specific. Maybe you own a forum about web design, and one about programming, and one about web marketing, and so on. Now you create a webmaster related search that searches across all 5 of your sites. You now have a good chance of getting your users to visit more of your sites than by simply cross-linking to them. I am sure there are lots of creative ways you can use this so put your thinking caps on and see if this is something that will benefit you.