The hydrus network client is a desktop application written for Anonymous and other internet-enthusiasts who have large media collections. It organises your files into an internal database and browses them with tags instead of folders, a little like a *booru on your desktop. Tags and files can be anonymously shared through custom servers that any user may run. Everything is free, nothing phones home, and the source code is included with the release. It is developed mostly for Windows, but reasonably functional builds for Linux and OS X are available.
The software is constantly being improved. I try to put out a new release every Wednesday by 8pm Eastern.
Currently importable filetypes are:
Audio is not yet well supported, but it is easy to launch any file inside the client with your OS's default program.
The client can download and parse tags from a number of websites, including:
And it can be set to 'subscribe' to gallery searches, repeating them every few days to keep up with any new results.
The program's emphasis is on your freedom. There is no DRM, no spying, no censorship.
If you would like to try it, I highly recommend you check out the help, which has an extensive 'getting started' guide. A copy is included with the release as well.