http://www3.towerhobbies.com/cgi-bin...&I=LXJC80&P=ML

Yup box of 100 blades.. cost ya 10 cents a blade..

At that price it's not worth trying to sharpen them.

I can tell ya how to do it using wet/dry sandpaper from 400-2000 grit but you'll need to build a sharpening jig and spend enough on paper to be halfway to a fresh box of 100.
Here's the link for sharpening if you still want to try. It's great for hand plane blades.
http://www.shavings.net/SCARY.HTM