Third parties cannot gain relevance without 1) building a base and 2) meeting the electoral threshold mandated for federal election funds and debate participation. In that respect, it is a pity the Reform Party (which met the critical 15% threshold in 1996) splintered into irrelevance, but such are the perils of building a party around a candidate rather than a platform. Meanwhile, third parties can and do elect candidates to state and local office. Not only does that build a loyal electorate through familiarity and a record of performance in office, but if the states are "laboratories of democracy," such local representatives today must necessarily be tomorrows national candidates. That is what so nauseates me about the Libertarians fawning over first Paul and now Gary Johnson, life-long Republican office holders who only turn to the Libertarians when the Republicans will not have them. Same deal with the Greens and Cynthia McKinney four years ago (though she had the added liability of being a paranoid bigot.)

Parties are built from electoral and then policy results, but the latter necessitates the former. America has a surprisingly strong history of such third parties in both the original GOP and the Progressives TR and later LaFollette led away from it when it became too indulgent of laissez-faire business. Both third parties achieved substantial policy results that endure to this day (though the Reform Partys failure to block the NAFTA and WTO, or at least hold them to the standards expected of US business, threatens the Progressives achievements.) At the very least, voting for a third party that represents ones views allows the ability to vote ones conscience when neither of the two major party candidates do so.

I do not expect any third party to do well nationally until/unless America has Instant Runoff Voting, but grass roots party organizing/voting can provide the necessary support to implement such laws by state referendum. The 1992 and 2000 elections have liberals and conservatives alike living in fear of the spoiler effect IRV eliminates. Both major parties know that well enough to unite in opposing IRV, but at the grass roots level major party supporters have a vested interest in such laws (e.g. preventing another Clinton elected with 42% of the popular vote, or Gore losing despite a popular majority.) The real traction can still only come from third party supporters who know their preferred parties can never gain national office without IRV. However, those so inclined will never consider it practical if NO ONE votes for third parties, ever.

Ultimately, if you feel neither major party represents you, you should vote for a third party that does; there are enough of them you can probably find one, but if nothing else you can write in your own name as protest vote. If you feel that is just "throwing your vote away," then you can choose the lesser of two evils in one of the major parties. Either way, there is NO excuse for not voting at all. All that means is that you are content to let others govern you without your input, or that you deny the legitimacy of any government not chosen by you alone. Neither position has any place in a representative democracy or republic.