Cable length

How long can ide, monitor and power (pwrsply) cables be? I know that a monitor needs an amp after a certain length of cable, but what's that length. What I want to do is make a chair/desk/computer type thing, have optical drives on the arm rest and mobo like maybe mounted on the back of the chair.

The longest IDE cable I've seen is 36". I believe ultracable.com has them (not positive though), but they are the best cables, and reliable suppliers.
I have a monitor running on a 10' extension cable now with no problems/ill effects, and no amp....get crazy. I found a dual shielded one at the local computer show for $25.

For the psu, there are extension cables around, I've seen them in 12" size but can't seem to recall where. If you end up making your own, use heavy cable to keep the wire from heating up from the amperage being carried, and solder/heatshrink your joints.
Of course, double-double check your color to color alignment, wouldn't want 12 volts on a 3.3 volt line.
Personally though, I'd try to work out how the mount the psu next to the mobo, and extend only the drive power cables.

Have fun, man.

I've never had it happen personally, but have read several times of data loss occuring with IDE cables over 28". Perhaps the high-quality cables mentioned by Diggrr are a prevention against this happening.

Perhaps yes. I've heard of data loss too.
I only use their 18" cables (ATA133's for everything but the floppy) with the center plug removed, so each drive has it's own cable.