C64 random, and a thought (yikes!)
The C64 used a pseudo-random number generator on-board the SID chip to produce white noise. I would assume that, given the technology at the time, this sequence would be easy to deduce.
I was thinking along the lines of the digital noise in a computer to provide random numbers. How about a simple USB-based (or even chipset based) RF receiver which uses some unused or used frequency from which to derive randomness. I imagine that the white noise in an unused frequency would generate crypto-sufficient randomness. It might even be enough to continually scan through the FM or AM radio bands. If an FM receiver can fit in my cell phone with all its other gadgetry, I would think that it could fit on a motherboard.
Considering the proliferation of 802.11g these days, maybe even using the output of a spectrum analyzer of the 2.4GHz band could do that (and then somehow avoiding the inevitable privacy concerns with active intercepting WiFi, and the potential hacks to actually listen in.)
For the scanning idea, maybe feeding the input into a state machine which would dictate which direction the scan would move: up, down, up by x, down by x, stay, etc.
And what about that idea of a sound card sample? Imagine a microphone on a sound card in a server room or data center. PLENTY of noise in there from fans, air conditioning, and the like.