The Hydrus network client is a desktop application written for Anonymous and other internet-fluent media nerds who have large image/swf 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, and the source code is included with the release. It is developed mostly for Windows, but fairly functional builds for Linux and OS X are available.... More Info »
The software is constantly being improved. I try to put out a new release every Wednesday by 8pm Eastern.
Currently importable filetypes are:
images - bmp, gif, png and jpg
audio - mp3, ogg and flac
video - webm, flv, mp4 and wmv
misc - swf and pdf
Audio is not well supported yet, but for anything that doesn't work, you can easily launch any file in your default program from inside the client.
The program's emphasis is on your freedom. There is no DRM, no phoning home, no censorship.
If you would like to try the program, I highly recommend you check out the help. A copy is included with the release as well.