Pat alerted us to a new Page Rank update. I really do not pay much attention to the PR bar anymore. At best it is a glimpse into the past about 4 or 5 months. And at worse it is a fabrication. (I tend to go with the latter).
Simply put in an ungeek way, Page Rank is the relative importance of your page. In the old days it was hugely responsible for big SERPS in Google.
Today, many believe it simply does not exist, or is not very important. I believe it is still important to a certain degree, its just that Google no longer hands us the odometer to see how to manipulate them. Go figure.
Page Rank is part of linking and linking is the single most important thing you can do for your website. Of course it goes without saying that you should be updating your site with new content.