What will I need to get started with my new DSLR?

I recently got a Nikon D3100 with the 18-55mm kit lens.
I'm thinking about getting a UV filter for it, but I'm not sure about the size. I keep reading 52mm is that correct?

Also, are there any other accessories you recommend I get?
I don't see anything about a USB for transferring photos/videos from the camera to computer, do I need to purchase one separately?

The UV filter for the 18-55 mm lens is 52 mm.

I would further suggest you buy some 4 gb memory cards. Can carry formatted spares in your pocket so you don't get tempted to delete images to make room on a filled card (the most common reason cards become corrupted)

Your 18-55 most likely has a 52mm diameter, however, check on your front lens element, it may be 58mm.

Here's a guide for "Buying a Filter For DSLR Lenses - http://www.the-dslr-photographer.com/2010/03/buying-lens-filter.html