I like overkill, I guess. Currently running an Antec TruPower 550, I'm seriously considering putting 2 power supplies in my case. I think I'm approaching server status with all the drives installed, not to mention all the fans and other power grabbers, and I want to add more drives. I have the room in my case, but can't seem to find any information through the search engines on how to go about doing it. A relay on PSU #1 to power up #2? Any information (a link maybe?) would be greatly appreciated.

If you feel you need this then get a redundant PSU. You don't want to connect two PSUs together. Will cause many issues. I think you are going off the deep end. I believe a typical HD draws about 13watts.

Take a look at this article in PC World concerning power requirements. Your 550 watt PSU is more than enough power for anything you can fit in a PC tower.
http://www.pcworld.com/howto/article/0,aid,109379,pg,2,00.asp

Unless it dies,

In which case a redundant supply is nice but you need the motherboard to do it....a server class motherboard. Of course the same could be said for the processor and the board etc etc.

Jimi_l

Power estimator;

http://www.jscustompcs.com/power_supply/

Fans draw about the same current as a night lite (4 watts)

As was stated your current power supply will serve you well.
If you're concerned about fans and show items drawing too much power you could do what I did. I robbed a 100 watt power supply out of a otherwise dead old compaq. I jumperd the green wire(power on) to a ground wire. This turns the PSU on. You can put a switch in line here but I didn't bother. I then snaked the molex plugs thru a knock out in the back of the case and connected the fans and show items. I used automotive wire covering to clean up the appearance. It ain't pretty but it works.

I may be crazy, but I'm not stupid...

Thanks you all for the responses. Helped a lot.
--Setishock - pretty has NEVER been a consideration! LOL
Thanks again, y'all!