I've painted my room with three walls white and one wall a very deep blue

Ive also got a wooden floor

What colour furniture i.e. desks, cupboards should I have to make the room look effective?

Go to this site and play around with paint colors:
Sherwin-Williams - Discover Color (http://www.sherwin-williams.com/visualizer/)
It will show 2 coordinating colors to go with the color you choose.
Roycroft suede and tan. Choose light colored wood furniture and paint the shelves suede.

Blue can be forgiving, but there are colors you should steer away from.

For instance, no blue furniture. ;)

White is safe, but will be lost because of the three white walls. Beige is also safe, but may blend too much into the floor.

Every room should have a touch of black, just to ground it. That doesn't mean a large piece, but a black couch or love seat may not be a bad idea.

Pictures on the walls also help.

As for furniture, wood is always nice, as it can be sanded and stained when you change paint colors or other décor. Just make sure that any furniture you buy is solid wood, not veneer. You'll pay a bit more but your furniture will last forever.

Really it's up to you and your style.

I'd love to see a picture of the room, then I could give you better suggestions. :)