If you don’t have access to Visio or AutoCAD, OpenOffice Draw is a free* program that you can use to create signal flow drawings. One of the best features is being able to make a connector between objects, which lets you reposition items on the screen while maintaining connections.
Check out the video to see how I use OpenOffice draw:
*check the licensing requirements of OpenOffice draw, as your usage might require a paid version.
What is your favorite drawing tool, and is there a single feature that makes it more useful to you?
The program I use for all my drawing needs is AV Snap. It is a free program developed for the AV industry but can be used for any drawing application.
http://www.avsnap.com
ProAV School should do a training video for this program because it is very powerful and free. Or maybe you could talk to the developer to see what resources are available.
You ask what drawing program we use and I had try to post a comment about 100% free program that has a lot of features and was designed for the AV industry.
AVSnap and can be downloaded at avsnap.com