Yep zip ties (or, as they might be labeled at the store, cable ties), will work wonders. Useful for both bundling up the wires a little, and then attaching them to various points (so they won't flop all over inside).
Rounded cables, for the hard drives, optical, and floppy drives also.
After that, for some of the little cables, like for the fans that power off the motherboard, wrap the cord around a screwdriver, pen or pencil, hold it tight for a couple of seconds, and then let go. It'll be nice and twisty like a phone cord.
Try hiding some of the excess power supply plugs and cabling behind the motherboard panel, or up in an unused 5.25" drive bay.
For some of the small header cables and whatnot, I found spiral wrap works really well (now I just have to find more around town somewhere). Otherwise, possibly try some cable loom.
For power supply cable tricks, you can use larger diameter spiral wrap or cable loom, or get some cable sleeving and heatshrink. Frozencpu.com has a wide selection, good rating on resellerrankings also (never used them personally, YET--hopefully soon enough

).
Unfortunately I don't have a digital :camera: to take pictures with...