Labour vs Socialist: Labour was the traditional blue collar, socialist party, whereas the SP was the radical, fringe left, originally Maoist(!). SP is still more to the left of Labour, but has seen through the past few years a slow shift towards Labour, losing the more radical points. Not to mention it has some really good ideas on several topics (I think).

CDA and ChristenUnie are somewhat alike: ChristenUnie is the more orthodox, and conservative version but with different ideas on economy, environment etcetera. There is interesting parallel between the SP and ChristenUnie: both parties are largely carried by their sympathetic frontman.

Fortuynism is the common Dutch term for the heritage of Pim Fortuyn's ideas. Fortuyn's former party is dead, and is polled for years now on zero projected seats. EenNL is the reincarnation of two former Fortuynists, Marco Pastors and Joost Eerdmans who are both outspoken on the immigration debate. Pastors is a populist, Eerdmans is more of an academic. Sallient detail: rumours have it that Rita Verdonk has had talks with EenNL.

Wilders broke from the VVD when the party decided negotiation for accessions of Turkey should begin, somewhere 2004. There had been previous disputes, but Turkey was the breaking point. One more conservative, if not extreme, voice on the right. Most of his ideas are brazenly aclash with the constitution. As you see, EenNL, Fortuyn's party and Wilders have splintered the hard right to pieces. None of the three parties have been projects with many seats.

Liberal: in the European liberal version, both economically as philosophically. Also see: http://en.wikipedia.org/wiki/Liberalism_in_the_Netherlands

The ChristenUnie people are more deeply religious. Sometimes they have suprisingly liberal positions. The CDA also incorporates the Catholics, and the Christenunie is formed out of a number of smaller, less mainstream protestant churches.

EenNL is sort of a split of the Fortuyn party. Fortuynism is the politics of the murdered Pim Fortuyn. It's a kind of patriotic populism with a libertine twist. Sort of like Sullivanism.

The VVD was being too middle of the road for Wilder's tastes under the leadership of Jozias van Aartsen, which is why he went away. He may also have daydreamed about making a similar kind of breakthrough as Fortuyn managed, but he doesn't have the required charisma. The VVD has since veered right and back left again. Currently, they're still a bit more right-wing than they were under Van Aartsen, but also more modern.

A liberal in the Netherlands is someone in the general tradition of Adam Smith, John Stuart Mill and John Rawls (in Dutch history Thorbecke is the most important liberal, certainly from the VVD viewpoint). There are a lot of different viewpoints expressed in that tradition. Generally, liberals are modernist in the sense of believing in progress, areligious, and most believe in the free market. Liberal doesn't have the left-wing connotation that it has in the US (don't know how it is in the UK), nor the libertarian connotation of neo-liberalism (although both liberal parties are pro-market, only a wing of the VVD is really neoliberal).

Specifically, the D66 party came out of the progressive movement of the '60s (as the name indicates), and the VVD is a continuation of one of the oldest political parties, after several splits and recombinations. The VVD is something like the party of business and the middle class. D66 is on life support. There is a new party called LibDem, but I don't know if they made it.