I used to share my web marketing instructor's sentiments about the popular professional networking site LinkedIn. Few people I knew used it and it seemed like every time I was on the site it was trying to get me to sign up for all these useful yet costly features. The entire point of the site is to network and perhaps find a new job but how often are we career seeking.
So now my opinion has changed because some of the features on the site are pretty cool. The one I like the best and not because its free is the feature that shows you who has been viewing your profile. It is not a teaser either like the silly Facebook questions and answers that pop up and say "someone thinks you're cute!" as you anxiously click on it to find out who it is only to be disappointed at the fact that its your buddy trying to click on enough questions to earn coins to unlock answers about himself. The feature on LinkedIn shows you either a user from an organization for example someone from the Chrysler Corp or a specific profile that has looked at your profile.
I also like that you can link the profile to another web page which makes it nice for sending resumes or links in an email to potential employers instead of a resume. I have only done this once though and I'm not sure if anyone that I sent it to actually looked at my profile.
I have also just downloaded the LinkedIn app for iPhone. It has a neat feature that lets you connect with other users accounts if you are in-person with them simply by putting your phones close enough together. The native API is also nice. I hate when apps just use the safari browser built into an Apple device. The only drawback with the in-person connection feature is that you need a bluetooth connection to make it work. Make it work over WIFI and that would be much better if not on 3G. I also like that you can easily change to one of several different color themes on the app. If you are into the LinkedIn site the app is pretty good if you have an Apple device.