LinkedIn has been doing this for a while and I just noticed it on Slideshare as well: alerting users to the completeness of their profile.
LinkedIn
This strikes me as a very subtle yet effective way to get your users to provide more information about themselves in their profile. Who doesn’t want to get to 100%? If there is underlying value to the user, it should really accelerate completion of user profiles by raising awareness and granting some Pavlovian eye candy as well.
SlideShare
If your site invites your members to submit profile type data, you could do worse things than to add a percent complete status bar to your interface.
C. David Gammel, CAE 
This really is Pavlovian. I’ve found myself adding info to my profiles in several places, to make it more complete … although a couple of systems ask for information on your personal life that I just don’t think would be interesting to others in a professional networking group, so in that case I just have to live with a low percentage of completion. =)