LocoBuffer
From Jmri
[edit] RR-Cirkits LocoBuffer II
Is available from here.
Unfortunately, it appears that the new USB version doesn't work yet with Linux or MacOS.
FTDI promises a Mac fix as soon as they have someone that can work on it. (from an FTDI message dated 13 Feb, -06) My son qualifies as a Linux Guru, and he has promised to work on the Linux driver as soon as I can get him a unit to test with. [Dick :)]