The national Libertarian Party has set up a web page for recognized candidates for the Libertarian presidential nomination:

The Libertarian Party recognizes 2016 Presidential candidates who have campaign websites, are dues-paying members of the LP, have met all U.S. Constitutional requirements to serve in office as president, and are not running for the nomination of any other political party. They have filed with the Federal Elections Commission, with the exception of Darryl Perry, who has chosen not to file as a protest against the FEC, claiming it lacks constitutional authority.

Another source for listings and information about possible LP candidates is the Independent Political Report.