Reddit mentions of Visible Dust EZ Sensor Cleaning Kit with 1 ml VDust Plus Liquid Cleaner &4 DHAP (orange) 1.6" size Swabs

Hair, dust and smudges on the focusing screen, mirror or viewfinder are the worst. They are annoying, but because they don't affect image quality, it's usually not worth having it professionally cleaned. So what we usually do, is just learn to live with it...until it does get so bad that a cleaning is actually worth the cost.

The focusing screens on these lower level DSLR cameras aren't meant to be user replaceable, but I do believe it's possible. You may even be able to clean it without removing it. I'd suggest the same type of kit that you'd use for sensor cleaning...a sensor swab and some cleaning fluid like eclipse etc.
http://www.amazon.ca/Visible-Sensor-Cleaning-Liquid-Cleaner/dp/B002XJ3JL8/ref=sr_1_1?ie=UTF8&qid=1382987682&sr=8-1&keywords=sensor+cleaning+kit

Initially I'd try something like a "Rocket Blower"

If the dust persists, you'd need to look at some deeper cleaning products like the "Visible Dust" or "LensPen" gear.

Beyond that you can send it back into canon for a full service and clean.

I start with a blower, and if that doesn't work, then I use this: http://www.amazon.com/Visible-Sensor-Cleaning-Liquid-Cleaner/dp/B002XJ3JL8/ref=sr_1_1?ie=UTF8&qid=1398045474&sr=8-1&keywords=DSLR+sensor+cleaning+kit