Todd is right. You're knife should full fit in the board diagonally from corner to corner. My current board is 18" x 16" x 2" and I love it, but I was able to work just fine on previous boards that were 10" x 16" x 1" and 12" x 12" x 1" with my old 8" chef's knife. I would also recommend getting the largest board you can feasibly fit on your counter/work area. I measured the space I had and bought my current board based on that, leaving room for the can opener and utensil holder that would sit behind it next to the wall.
Like Todd said, a true butcher's block is usually much thicker than a cutting board and many have feet. They will function just the same though. The thickness is probably to accommodate heavy chopping like a cleaver through bone. I think there are also some boards labeled as blocks when they are around 2" thick as well, but I don't know that they would actually function as a butcher's block or if it's just marketing. Either way they will function the same for a knife regardless. Just get one you think looks nice be it a board or a block. If the board will be right at the edge of the counter top the thickness may not be an issue, but if it will be further in with the lip of the counter sticking out you might want an inch or thicker board for clearance. I find it helpful for horizontal cuts, but that is just me.
I personally love end-grain boards and blocks. They look nice and are easy on knife edges, plus they have better self-healing characteristics. Once you cut the grain on an edge or side grain board, it is cut. An end grain board is more like cutting on a very dense brush. The fibers are more likely to move to the side or split and can come back together making for less cuts and scratches on the surface. Just make sure that if you get an end grain board it is no coated with a varnish. You want bare wood treated with oil and/or beeswax or something similar. Varnished boards look nice, but it defeats the self healing properties (you will see cuts and scratches VERY quickly) and it can also chip off over time making for a spotty finish on the board.
I also second the waste bowl idea. In my kitchen the trash can cannot be kept close to where I prepare the food and cook, so the bowl is a great time saver. Plus, if you get a nice decorative one it looks nice. A smooth glazed flower pot works as well, just don't use a bare ceramic one as they are absorbent and you don't want that. lol I personally just use a white glass mixing bowl with a design on the outside. Easy to dump and rinse out after I'm done.