Low cost compressed air system to clean PC

[#1]

I baulk at the cost of aerosol cans of air-duster or similar even though is useful to keep the cooling fins of the processor heat sink dust free.
After years of careful research I've developed a environmentally friendly alternative. It is pictured below:

You attach one end to your mouth and puff.  Further research is required to prevent too much spit traversing the system, but on the whole it works well.

[#2]

I use an alternative which doesn't have the spit risk - mind you it isn't recommended for dusting the motherboard, graphics card, etc.

[#3]

You can get a small 'bottle' with two tube connections in the top (one tube usually extends a bit into the bottle) - these are sometimes sold for collecting small insects by sucking but will work in reverse, any unwanted moisture will collect in the bottle and not be blown on your expensive equipment.
A bit more costly would be to get a tyre valve depressor (off an old foot pump for example) and connect this to a spare tyre (nice reservoir of compressed air), fit it with some kind of simple valve (maybe an aquarium air pump fitting).  In the early 1970s some Volkswagen cars used the pressure from the spare tyre to pressurise the screenwash bottle.

[#4]

My local £-land had the aerosol dusters in - got one then.

[#5]

I Have one of these for cleaning my camera which also doubles up as a keyboard cleaner.
True it's nowhere as cheap as other ideas previously posted,
http://www.the-digital-picture.com/Reviews/Giottos-Rocket-Air-Blower-Review.aspx

[#6]

I have a neighbor who has a compressor  i just jump across the fence tower in hand 

[#7]

Fence leaping with a PC Tower in arms?  Isn't that an Olympic sport?
ps A small additional advisement on my low cost compressed air system as described above: Don't suck!

[#8]

4C's computer cleaning DIY vacuum adaptor.