Whirlygig is a USB 1.1 device that contains a fast, high quality hardware random number generator. Via a Linux driver, each whirlygig you connect makes available an additional 7Mbits of high quality randomness a second, or 750-850KBytes/sec sustained using the standard /dev/hw_random API.
It gives you a high-bandwidth source of non-repeatable, non-guessable, evenly spread random bits. The RNG is believed to output numbers very suitable for hard crypto (although note as it is made available under GPL2 I don’t warrant that this or anything else is the case). Unlike many PRNGs, it should not be possible to reverse the RNG state in any usable way from observing the output. Because of the high bandwidth, it is suitable for generating very random numbers for statistical simulation purposes, which should not show any spectral aliasing with your data.
The Linux rng-tools package includes test code and a daemon which transfers entropy from /dev/hw_random into /dev/random, effectively giving you a bottomless pit of standard randomness without having to modify any code using it.
Source: Whirlygig RNG