NFL Trade Rumors (NFLTR) is a pretty good website this time of year. They keep up with free agents, and, if you follow them on Twitter, you can get an alert on nearly every visit rumor, every signing, and any rumor about contract details, trades or changes in status.
Just about a week ago, NFLTR published an updated list of free agents: The (updated) Top 50 Available Free Agents List.
The first name on the list is Ndomukong Suh, but the third best free agent still available as March draws to a close is — according to NFLTR — Zach Brown.