I'm getting what looks like a small hair in the viewfinder of my DSLR. It shows up in different lenses and does not appear to be on the sensor (cleaning the sensor doesn't remove it). What can it be?
Can you see it in your images? If you can see it its probably on the sensor. But if you don't see it it's more likely in the mirror of you DsLR. Try to use blower to your mirror, if it is still there wipe it with a gauze pad that is for DsLR use. Wipe it from one direction only (Imagine your a surgeon who's doing an operation with sterility caution)

(I know this doesn't help, but can't resist) I'd say it's Francoise, Don

Are you sure it's not in the view finder itself?
Yes. It was on the mirror. I blew it away with my rocket blower.
Do you have a link to that blower? I was looking for something to clean my mirror too.
Look up Rocket Blower on E Bay.
There are blowers that they can intake air on the same tip. Better get a Blower that blows only on one side and get air intake on the other side or else you will be intaking those dust blown away from you mirror and setting them back in.