I like seeedstudio, they are creative, open source and geared towards tinkerers. The Crazyflie is a great example if why this shop stands out. It's a tiny (90mm square) quadrocopter. And it's open source, in fact seeedstudio is counting on the community at large to develop it. It's controlled via a 2.4ghz link and a PC. And it can be wirelessly updated if you don't have a jtag debugger. Based on a STM32 ARM cortex M3 running at 72 MHz, its got a lot of processing horsepower. Check out the video!
Build your own swarm, I wonder if you could get a camera small enough for FPV. This little guy can fly around 7 minutes on a charge, and can lift around 5-10 grams.
Starting around $116