News: I've released fsrw1.5 which fixes a bug in nextfile() when the root directory expands to be larger than the cluster size.
Here's some code to support FAT16 filesystem reading and writing from the propeller, as well as some low-level Secure Digital block I/O code.
The current version (download here) is 1.5, last updated 7 April 2007.
If you try this code please send me email (rokicki at gmail.com) on how it works for you and what is lacking that you need.
More details on the code can be found here.