Source for inexpensive glass hole saws.
 

Hi Tech Glazing
#210 13060 80th Ave
Surrey, BC

(604) 501-1212

About 4 years ago I bought a hole saw from these guys and got about a half pound of cutting compound (grit) the hole saw is 1 1/4in and worked great. I've drilled probably 30 holes with it and just found the company again today. They are getting out of the cheap ($25) saws but will order them in for people but you may have to pay a shipping charge. If a few people wanted to order them together you'd save that charge. The only downside to these is that you NEED a drill press and a bit of patience. To drill 1/4 inch glass took me about 5 minutes per hole but on a 10-15 gallon tank the holes took about 2 minutes.
The saws wear out but mine still has about 3/4 left so like they said at the shop the saw should last about 100 holes give or take a few.

Doug

Check out THK diamond tools on E-bay.
I believe they beat the 25$ even with shipping included.

My understanding though is the diamond chips are glued on so the bit only lasts a couple holes. Granted if you are just drilling your own aquarium that would do but if you are drilling a few here and there....

Doug

The THK bits are actually a good quality product, not single use drillbits.

holes
 

I've used the ebay ones to drill about 10 holes so far of which some of them were through 3/4" glass. still going strong...