Documentation for Trisquel (or other libre GNU/Linux distros)

Hi everyone!

I remember a discussion I recently had about documentation and Free Software.
One critical thing that turns people off or might make it harder for a user to actually use some pieces of Free Software is a lack of documentation, which just so happens to be an issue that can be tackled by non-technical members of the community.

In this spirit, I'd like to ask all of you for suggestions on (libre) programs that (in your opinion) need more documentation, be it for setup, administration or anything that you feel is appropriate.
The focus of this should be on software that is already included with Trisquel or other libre distros in order to make them more approachable, but I'd appreciate suggestions for self-hosting guides for certain applications etc. as well.

If requests come up for something I'm confident writing about, I'll take the time to try and write documentation (be it a guide, tutorial or something similar) myself.
Apart from adding the Trisquel-specific information to the wiki, I can host the rest on a small Debian server instance that to be set aside for this.

Please post with suggestions and whether or not you think it would be useful, if you're interested in providing something yourself and any other hints.