Last time I checked, I associated myself the most with Venstre (meaning "left", but they're a right-centrist party). That, or Arbeiderpartiet (workers' party, slightly left). Would have been more centrist if I could, but the only true centrist party we have mostly caters to farmers ("let's subsidize the farmers even more, and rise the toll on all foreign food, so all the farmers can continue being farmers even though they hardly produce anything!").
I agree with Høyre ("Right") in some cases, but disagree with them too much otherwise to vote for them. They're supposed to be the moderate right-wing party (in other words, slightly to the left of the US Democrats).
We also have Fremskrittspartiet ("the Progress Party"), our resident populist party which sits slightly to the left of the US Republicans (Imagine Republicants without religion). Those are the guys who propose to lower taxes on alcohol, petrol and cars, make tobacco ads legal again and spend the entire Oil Fund on building motorways and subsidize roads, as well as closing the borders for immigrants. For some reason, they have got a relatively strong backing in the population (currently at about 15%, according to polls, they peaked at about 30% a couple years ago). The stereotypical idiot in Norwegian culture votes FrP. To their credit, they've never been in a position of government, so it's hard to tell how their wacky ideas would have worked in practise.
We also have a number of smaller parties, from communists to fundamental Christians and the Coastal Party (all three polling in at about 1.5%). And remarkably less poop-flinging than we see in the US. Such a level of lies and bashing as we see from both sides of the debate in the US, would probably lead to expulsion from the party in Norway, and the guy would probably plunge on the polls and forever be remembered as a grumpy whiner.
I think a two-party system allows for too much polarization of the debates. Everything boils down to "Us vs. Them", and if you're politically engaged, you're either for or against one of the big parties. No political alliances, no third voice to calm the debate, and too much dogmatically voting against everything (especially in Congress, where practically everybody vote according to either the Democrats or the Republicans based on which party they belong to themselves).
Though, with more parties, expect to see poop flying in more directions than ever. But at least there are smaller quantities of the stuff around, especially around election time.