I used my dremel and a CAD template to make perfect octagonal holes- cut out on the lines, score, and fold back. Edges are clean and not sharp like you get from a drill or nibbler, and it looks very professional
...Or if you're like me, you take all this effork to make the holes look nice and perty, only to discover you can't fit the fans inside the case and have to mount them outside, completely defeating the porpose. DOH!
Pentium IV 2.4C Northwood- M0 stepping @ 3.2GHz HT
Air Cooled w/ SP-94 heatpipe & 92mm Vantex Tornado at 45C
4x256=1gb dual-channel 2-3-3-6 OCZ PC800DRAM @ 890MHz 3-4-4-8
MSI Neo2-PLS w/I865PE & SATA @ 4x267=1068MHz
BFG GeForceFX 5900@485/967MHz = 6284 3DMark2003s; dual-head 21" CRT & 19" LCD