TITLE: Non-computational software useful to mathematicians
QUESTION [38 upvotes]: The MathOverflow question Open source mathematical software contains a list of programs that are useful to perform various computational tasks, such as computer algebra systems.
However, evaluating complicated formulas is not all that a professional mathematician needs to do. For instance, another important part of it is communicating results, producing papers and slides. There was a Mathoverflow question devoted specifically to
tools for collaborative paper writing.
It would be useful to identify and gather on MO a list of areas of activities where research mathematicians can use software as part of their professional activity.
I think it would also be useful to gather on MO a list of software that does not strictly do computations, but is nevertheless useful to those who research and teach mathematics.
The first example that springs to mind is of course $\LaTeX$, but there is much more:

citation and literature management software, such as Jabref, Zotero, Mendeley
conference management software, such as Open Conference Systems (never actually used it, but it seems interesting)
reference tools such as the Online Encyclopedia of Integer Sequences and Plouffe's Inverter
Euclidean geometry software such as Geogebra
diff'ing and merging tools, such as latexdiff, kdiff3
specific LaTeX packages such as Beamer for presentations or several drawing packages (TikZ, Eukleides).

I find some of those real gems, and I'd like to find out more examples. So, the question is:

Can you provide (other) examples of programs that are useful to professional mathematicians in their job, while not being strictly speaking "software that does complicated computations"?

The question is a little broad and perhaps if there is much software relevant to a specific activity it will be wise to ask, based on input given to the question,  a more specific question. Also please do not interpret this question too broadly (see discussion below).
Also check these MO questions: Tools for collaborative paper-writing (mainly regarding revision control software), Most helpful math resources on the web (mainly regarding online databases of something).

REPLY [2 votes]: When collaborating in person, I frequently work at the chalkboard with my collaborator, periodically taking pictures of the board with a smartphone, and then posting the pictures in a shared Dropbox folder. That way, we don't spend our time together transferring notes from the board onto sheets of paper.
Most of my collaborators are employed elsewhere, so I wanted to replicate this experience for remote collaboration. Specifically, we wanted access to a common virtual whiteboard. Such technology is available under a freemium model with MIRO. When working together, we access MIRO via iPads while simultaneously chatting face-to-face on Google Hangouts. When the wifi is good, MIRO's virtual whiteboard exhibits near-zero time lag, which makes for a seamless working experience. To save our work, we periodically export the whiteboards as pdf files and save them in a shared Dropbox folder.
(As an aside, I've found that over time, I'll forget the mathematical context of various pictures in the Dropbox folder. It's extremely helpful to maintain a README.txt file in the same folder that provides a short description of the contents of each picture.)