A library called PlayStation File System Libraries (libpfsm) has been anonymously released.

What does PlayStation File System Libraries feature?

• Support for multiple simultaneously connected devices.
• Hot swapping of devices.
• Support for multiple partitions (with different FS).
• NTFS support
  • Alternate data streams
  • Sparse files
  • File compression
  • B+ trees directory
• FAT support
  • FAT12, FAT16, FAT32
  • Long file names (VFAT)

Writing to NTFS formatted volumes is not supported and not planned.

Check the README for everything else.

via PS3-Hacks