Libertarianism has become virtually synonymous with Capitalist Libertarianism (which is right wing by most peoples definitions, though they will tend to claim its not), because there are such a lot of them on the internet and they are such loudmouthed pains in the arse. But there are definitely other traditions that reject the basic assumptions of capitalist libertarianism yet still deserve the name libertarian, most of which would tend to be classified as left wing.