I and my fried SouJack are developing a new tool called PS2 PFS Explorer.
The tool will be able to read/write users partitions on PS2 HDD connected directly on PC.
Now, the tool is beta version and just able to READ the HDD data.
Screenshot:

Tool download:
http://www.egama.eti.br/download/ps2pfsexplorer.rar
To mount a HDD partition, just select the HD (\\.\PhysicalDrive0, 1, 2, etc... depending on number of HDD on PC) and click in "Montar Particao" button.
To "download" a file to PC, just double-click in file and select the destination folder.
We have tested in 2 HDD formated with WinHiip
The tools has in beggining and has much to do, but is the start....
We thanks any comments, tips and sugests.
Thanx for all.