http://board.flatassembler.net/topic.php?t=13741&postdays=0&postorder=asc&start=40

Shows a PRNG implementation based on Rule30 http://en.wikipedia.org/wiki/Rule_30, a really simple but interesting algorithm brought up by @tthsqe

It's efficacy wasn't tested, but I thought it was cool.

There's also the PRNG used by PROE which was tested for randomness and has very good throughput. But you'd have to pull it out of the encryption code. http://board.flatassembler.net/topic.php?t=6518&postdays=0&postorder=asc&start=0