I'm sure you can all appreciate the importance of switching on and off your equipment in the correct order. Even knowing this, I still make mistakes! And when the studio is being used by external engineers I have no assurance they know what my preferred order is, nor would I expect them to.. well, better have all that taken care of and be easier for everyone, and more reassuring for me
This is a very basic design, and a hybrid of the information I found around the net
You can use as many stages as you desire, however each stage including relay required approximately 100mA, so if you're going to be doing any more than 10 you should look at building a higher current power supply. Now I got all my RC constant values by experimentation, which is why some of the values are all out of wack. It might be smarter and cheaper to used a fixed capacitor value and vary the resistor, actual calculations may help you zone in on the results you aim for. The attached schematic is for a five stage design, with approximate 2 seconds between stages for the first four, and then about 10 seconds for the fifth (which is where all speakers and amplifiers should be powered from - this should be enough time to let the electronics before settle)
What makes this design different to all off the shelf I've seen is that the stages can be used to switch power from anywhere. All others I've seen provide switched outputs from the power running into the sequencer. But what if you have your digital gear on one circuit and analogue on another? Or like me I'm running a few balanced power transformers, other sequencers I've seen couldn't work. Just remember you'll have to be very careful and safe in building this as all those relay terminals are active with 240V when connected, even if the device is off, and if you're switching different phases then you'll have 415VAC in there
Any questions don't hesitate to ask!
Schematic: http://img220.imageshack.us/img220/9596/sequencesch.jpg Part numbers relate to: http://www.jaycar.com.au **all diodes are 1N4004 
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and a fun (and pain in the ass) build!
