I have a "thin station" computer donated to me by Devon IT. This has a 433MHz VIA Eden CPU and a 128M Compact Flash card, no hard drive. No fan either, the quietness is spooky. This computer is remarkably similar to the laptop developed for the OLPC project, so I made some customisations to my new-generation Puppy2 to optimise running within the limits of the OLPC specifications, in particular the 128M RAM limitation.
Puppy is designed for this kind of situation from the ground-up. Extremely fast, very small footprint, a full set of applications, limited writes to Flash to extend its life indefinitely. There are no compromises -- if you have read commentary about the OLPC project from various sources, you would think that an operating system and applications squeezed into such a minimal system would be severely compromised. Not so.
Page written by myself, Barry Kauler, the original developer of the Puppy Linux project. "Puppy2" is my next-generation Puppy Linux, soon to be in beta and very soon after that will be the official release.
Puppy home page: http://www.puppyos.com/"