Puppy Linux is another distro that does the same. It's one I've used before and is actually rather pleasant, and seems to "just work" for most anything. (including an awkward Windows-only USB wireless network interface) The interface can be a bit awkward though, admittedly, and it doesn't have everything available in its repositories, but it still works blazing fast.
I've used Puppy quite a bit, and didn't realise it was running in RAM. I have to say though, that I still think Tiny Core has the edge in terms of speed.
