Recently, my grandmother put in a large (2 basin) countertop sink. Lucky for me, the pallet it came on was quite similar to the size I had in mind, which was 2' x 6' (that's feet)! Also recently, my parents had a new deck built, and I convinced the contractor to let me pick out any wood that I wanted to keep, since he was going to throw it away anyways! I got a bunch of wood from that, to facilitate my project habit :P .
First things first, I chose the location of the desk, so I could test fit the table top in its approximate location. From there, I built a simple desk leg like structure. In the short direction, the legs are attached at both top and bottom for rigidity. The back legs are also connected by a long piece that would double as a foot rest (works great BTW). Since I had it right next to a doorway, I built it such that there were three legs, and the fourth would be held up by an angled support.
During the test fit, I decided I was going to cut off at least a 45 degree angle to allow for more space walking into the room, however when I went to cut it, I (on a whim) decided to make it more fluid. I free handed a shape and cut it with a jig saw. Next, I got pretty into the whole 'finishing' stage, because I thought it'd be cool. Turns out it's difficult, but the work you put into it usually makes it look that much better. First step of this was cutting a 45 degree angle off the edge all the way around. Then there was sanding. Lots of sanding. This was a pallet, and was stained some nasty red color, and mad of a lower grade of wood. There was a lot of sanding to bring it down past the stain and to a nice smooth surface.
What I'm not telling you here is that this was all done inside (stupidly). This is only bad if you don't have something to suck up the wood dust while sanding, or in my case, a shop vac who's filter had fallen off (doh). Let's just say there was a lot of room clean up after this bit was done, since the vac had just blasted the dust everywhere.
Lastly, for the professional look and durability factor, I applied several coats of Polycrylic to seal it. I also applied two coats of a light GoldenOak colored stain before the sealer. Definitely follow the instructions for preparation and between step methods for the stain and the sealer, because this can easily mess up the whole thing.
So that's it! If you have any questions about it, or the process, let me know in the comments, but don't forget, I'm no professional carpenter, but I had a blast making this!