One of the few pieces of non-free software I always needed on my system is a rar unpacker. Despite that there are very good free alternatives for high-compression archivers like 7-zip or tar.xz, many people seem to like relying on a proprietary format like rar and it's in widespread use.
Years ago, someone came up with a GPLed rar unpacker, but sadly, that was never updated to support the rar version 3 format. Its development is stalled.
For that reason, some time back I suggested to the Free Software Foundation to add a free rar unpacking tool to their list of high priority projects - they did so. Happily I recently read that they've removed it. There's The Unarchiver now, based on an old amiga library. It supports a whole bunch of formats - including rar v3. It's mainly a MacOS application, but it also provides a command line tool that can be compiled in Linux.
It needs objective C, the gnustep-base libraries and it took me some time to get it to compile properly. For the Gentoo-users: I already committed an ebuild, just run "emerge unar".emerge TheUnarchiver
Update: Changed ebuild name to unar, as that's the name upstream uses for the command line version now.
If you need help getting parts of the unarchiver to work, I've been working on its tar unpacker, so I usually have linux (64bit) executables sitting around. Great to hear it is getting adopted into use by people.
I'm not sure how new the newest release is, but if it's a while old, the current version from mercurial should contain vastly improved commandline tools (such as lsar, which now supports long listings that actually have some useful information).
It shall either directly depend on dev-libs/icu or >=gnustep-base-1.22.0 which enforces ICU useflag, when compiled against gnustep-base-1.20.1 which is at the moment stable it breaks on missing unicode/ucnv.h
and of course thanks for bringing this to the gentoo world :)