Libertarians are not liberals. There is in fact a Libertarian party in the US, though. There is a republican member of Congress from Texas (the only one to vote against the war, using the grounds taht a formal declaration was constitutionally needed) who was a Libertarian but moved over with essentially the same views to the republican party in order to get elected.
Liberals in the modern sense (Neo-Liberals or Progressives to adademics) tend to support more taxation and regulation and more expansive government programs (military excepted). Libertarians (or Classical Liberals to academics) support minimal government intrusion into people's lives, and thus low taxes, few programs, and little regulation of business or personal lives. They have utmost faith in free amrket systems to solve problems naturally (As in Adam Smith's "Invisable Hand" theory). They also tend to interpret the Constitution VERY strictly and literally, sometimes (arguably) anachronistically.
Conservatives vary, because social conservatism has aspects of paternalism built in that promote larger government, but fiscal conservatism leads to a moderate faith in the free market and a desire for low taxes. Thus, the views of conservatives regarding the size of government depend on the way in which they prioritize their sometimes-conflicting goals.
