In Canada there are really three ideologies. Americans tend to view anybody that is not a Conservative as being a Liberal.
In Canada, you have Conservatives, Liberals and Socialists. I won't get into what they believe but give you the very basis upon which they build all of their ideas upon.
Conservatives - their fundamental belief is that one should preserve as much as possible the current social, economic and political order.
Liberals - their fundamental belief is in individual liberty and the government's primary purpose is to maximize the amount of liberties and protect the rights of its citizens.
Socialists - their fundamental belief is in the equality of all people. Private property and the distribution of said property is subject to social control instead of the control of the individual in his/her best interest or by the free market.
Edit. When I say "in Canada..." it's just because the rest of the world differentiates between Progressive people (Liberals, Socialists), and Conservative people. But from what I hear in the U.S. anybody who is not a Conservative is a Liberal regardless of whether these people are Liberals or Socialists. I suspect this to be the case because there has never really beeng a big Socialist movement in the U.S. and people just assume it to be non-existent. But in Canada, left wing would refer to Socialists, right wing to Conservatives and the middle-of-the-road would belong to Liberals.
-GL