We are planning our first trip to cannon beach (oregon). Is there any good camp sites available? Also, is there any good crabbing / fishing locations? Where do we buy fishing license from?

Good crabbing locations?
Fodor's USA board is about the best crabbing location I've ever seen.
Don't believe me?
Scroll on down.

Oswald West State Park near Cannon Beach is one of the most beautiful car-camping places I know. I believe you need to reserve in advance. Look at the Oregon State Parks website.

I just returned from the area and Oswald West State Park is the best camping location! It's not far from Cannon Beach.

I think the crabbing beaches are a little further south but I'm not too familiar with them.

We always go crabbing off the pier in Garibaldi, which is a little fishing town about 45 minutes south of Cannon Beach. (But they only let you crab off of some of the piers, so ask, or look for signs.) There is also good car camping near there - just north of Garibaldi near the Bar View Jetty. If you're in the area during a minus-tide, there's also good clamming in Garibaldi. (And it's SO close to good ice cream - Tillamook Cheese Factory.)

Another, quirkier option that you might want to consider is yurting - you can see your options for that on the Oregon Coast at http://www.oregonstateparks.org/yurts.php

In any case, Cannon Beach is much more picturesque than the area I'm talking about, but I'm not sure about the fishing prospects there.