A former boss of mine cleaned his PC's at least once a year with an air pump intended for balloons. That thing was not too big (so you could put it in whatever angle necessary) and more than enough force to blow away any dust.
When I was searching for some kind of air blower one guy on a forum even suggested an inflated balloon with a straw in it to direct the air flow.
edit: now that I know what to search on, I see them for less than $3. Trouble is the $9 shipping.

Oh well. I'll see how the bulbs work out.
edit2: Ok! I found a plastic sport pump at Quill.com. $2.53 free shipping!!

I can always use the air bulbs to clean my cameras.
















