If you are going to be using a dual or multi-PSU setup for mining, water cooling, FPGA's, etc. then you might want to consider one of these adapters.
They are best if you run a computer 24/7. This is the "original" version. It works perfectly when jumping PSUs, but apparently not all motherboard/PSU combinations are compatible with ATX soft-power boot and power off.
More details can be found at the Bitspower website
as is the documentationFrozen PC
is selling them for $25 plus $10 shipping
I'm selling them at 3 btc shipped for each (in US)
Current stock on hand. All are brand new in the box.
7 x Orange
7 x Green
1 x UV