D66 is a political party in the Netherlands. It's an abbreviation of Democraten '66, and was founded in, well, 1966. It's the first party to choose for a balance between the environment and the economy and is a progressive social liberal party.
The current leader of the party is Thom de Graaf, and the party has 7 seats in the 150-seat parliament (the Tweede Kamer), 4 in the 75-seat Eerste Kamer and 2 in the European Parliament.
D66 stands for personal freedom and the ability for people to lead their own lives by their own values, and they're supporters of the unalienable right to the freedom of speech. Following from that, they also support the right to self-determination over your body, supporting euthanasia and abortion.
During the 2002 elections they opted for new educational and healthcare system, as there were huge problems finding teachers and doctors. They also wanted to increase the budget for culture and change the policies for the WAO (Wet Arbeidsongeschiktheid, Law on the Incapacity for Work) so more people with disablities can get better jobs and simplify the tax system by scrapping allowable deductions in exchange for lower rates.
Sources:
http://www.d66.nl/
http://www.eerstekamer.nl/
http://www.tweede-kamer.nl/