As far as how-to-make-yourself-look-good-online-to-employers guides go, this one from Mashable is pretty damn good:
If you haven’t done this — even if you aren’t applying for a job — go do it now. People are out there looking for you whether you’re looking for them or not, and you don’t want them to find a big, sloppy mess (or nothing at all, or someone else).
I’ve been approached for jobs based solely on my online presence, which is a pretty cool thing to have happen. I treat Google results for my name the same way I treat dressing for a job interview — which is to say, I act like it could happen at any time.
If you’re still not convinced, consider this (again, from Mashable):
Of the almost 80% of U.S. hiring managers who had searched for candidates online, 70% of them said they had rejected a candidate based on what they found in his or her search results, according to a 2009 study commissioned by Microsoft.
This isn’t a weekend project. Go start working on it.