If you haven't seen it already, definitely check out Chris Brogan's free ebook, Personal Branding for the Business Professional. It's a quick read--mostly bullet points--and sums up some excellent strategies for building your professional reputation online.
There's a lot you need to do offline, as well, like working to make yourself a career untouchable. I'd also suggest exploring the Total Leadership model. This is something I'll be using in the Nonprofit Roundtable of Greater Washington Future Executive Directors Fellowship I'm helping to lead over the next several months. I plan to write more about the Total Leadership approach in the coming weeks, but for now, I highly encourage you to take a look at the model.