when backpacking my way around the world, i've found that it doesn't pay to buy beach towels as you go. even though they can be acquired cheaply in many places, the cost does add up eventually, and the cheapie towels tend to bleed colors all over your favorite t-shirts (or if you're not wearing a t-shirt, it will add some goofy colors to your back). as a result, about one month into my trip, i bought a good-quality normal beach towel and started lugging it around with me, despite the added bulk and weight of that much cotton. that changed when i was at a surf-supply store in dubai and discovered billabong's microfiber beach towel.
while microfiber towels are nothing new (REI has a great lineup of them, and i use the REI MultiTowel Lite - Large every day on the road) especially for backpackers and hikers looking to reduce the bulk and weight of the always-necessary towel in their pack, but the microfiber beach towel is a whole other thing. (while you can always use regular microfiber towels as bath towels, they look pretty damn dorky on the beach, and they tend not to be as comfortable as regular towels.)
but then billabong had to release their own microfiber beach towels which feel like regular beach towels, look like regular beach towels, but are lightweight, pack down into a small ball, and come with their own mesh bag to stash them in your backpack with. i don't see a lot of them available online yet, but these are really great for backpacking your way around the world's beaches.