They are automatically on the ballot in D.C. now, thanks to a good performance in this election.
For all the trash talk about D.C., I think people would be surprised at how many libertarian or libertarianish people thrive in this area. It makes sense, of course. Where else are you going to pitch a blueprint for radical social engineering of public institutions that you just know will work wonders for the lives of the American people? D.C. is pretty much where you can make a living pushing social engineering schemes.
The other thing that's interesting about a lot of libertarians I meet (and that may be because I meet them around here) is that they're fascinated by politics, despite a lot of pretensions to the contrary. I think many get in the movement by getting hyped up about politics the same way a conservative or liberal would, and then deciding that conservatism or liberalism per se isn't quite for them.
It would be interesting to see a map showing the distribution of self-identified libertarians. Of course New Hampshire would be a hot spot, but I expect D.C. would loom pretty large as well.