Self, I'm glad you asked that question, because DSLR video is becoming the norm, it would seem, and it's going to be really important to know the answers to such queries.
Luckily for us, Andrew Schär conducted this test the other day and posted the results online for all to see (image above). For the test he used his Canon 60D, 600D and 7D:
If you are shooting video with your DSLR you should use the following ISO settings: 160, 320, 640, 100, 200, 400, 800, 1250, 125, 250, 500, 1000, 1600, 2500, 2000, 3200, 4000, 5000, 6400
There's even a video of the test, which sees him ramping up from ISO 160 all the way to 6400. The noise gets noticeable, for me, around ISO 1600.
The music is quite catchy! The test, valuable video shootin' knowledge. [Wiegaertner Films]