One of the simplest ways of using LinkedIn is just as a "modern Rolodex" a list of the people you want to communicate with on a regular basis so that they remember you're out there, what you have to offer, and why they like you. The only tools you need for this is your LinkedIn profile, sending LinkedIn invitations to people you know and an hour per day to make phone calls. One of the biggest challenges for a freelancer or consultant is just making sure people remember you when they need something you offer. These quick check-in calls (with an appropriate time lapse in between) are a great way to just stay on your prospect's radar.

Of course LinkedIn search is also a great tool for this