Mounting a PCB in an Extruded Aluminum case
For extruded aluminum, find the local distributor for aluminum structural framing in your area. Try 8020.net in the US and Bosch-Rexroth in Europe. You might also try frontpanelexpress.com, though their stuff might be too big.

Here are some options to mount the PCB:


The slots
PEM studs (you'd need a fabricator to press these in for you)
Bolts and standoffs (try Digikey)


For the PEM studs, check out the KSSB family-- they're designed specially for mounting PCBs without extra fasteners.