Frequent readers may recall me posting about a donation funded port of TrueCrypt for OS X. The group just published their first update.
It sounds like they're taking on a bit more than a simple TrueCrypt port, as the post notes that:
...we realized that this project will not be a simple port of truecrypt to Mac OS X, but this will provide a multiple enciphered disks support encryption platform for the Apple operating system.Right now the project has a simple XOR'ing kernel module, but progress is being made. I continue to hope that TrueCrypt support of OS X becomes a practical endeavor through this project.