If those kind of devices interest you, I'm quite intrigued by the IDQuantique ones that are based on quantum physics to generate randomness. They have a USB product that has a random stream of 4Mbits/sec and is used by lotteries and gambling sites.
Intel has a patent on a TRNG that has a throughput of 2 Gbps+. They published a paper on its operation in JSSC a while back [1]. It passes all NIST RNG tests and is PVT tolerant. Too bad it's patented...
[1]: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6...