I am using degisy tdatafile: http://www.torry.net/quicksearchd.ph...file&Title=Yes

Using sections you have a flat directory structure. (and you can always cheat using / in the section name :-) )
I modified it a bit to support lha compression also.

The only problem is that when deleting a file the archive size does not become smaller. Only copying all files to a new archive helps for that.

Currently i am thinking of moving to sqlite for this purpose. Yes using a database for file storage :-)