I’m hoping this might be useful for other folks out there as well (especially the MATLAB wizards), so I’m making it available for download. If you think there’s something wrong or missing, let me know in the comments and I’ll try to fix it.
Download the DFT Cheat Sheet.
If I find the time and motivation, I’m planning on doing something similar for the regular Fourier transform (probably without the images) and for some of the more important trigonometric identities, since I find myself looking this stuff up in Wikipedia all. the. time.
last posts in signal processing:

What did you actually use to create the graphics?
Mostly Mathematica, with a little polishing in a vector drawing software. The math is set using MathType (I would have used LaTeX, but I was too lazy).
Also ne, jetzt also auch noch Spickzettel. Bis zur ECOC