After building all of this, I learned that only type SO cable meets code for entertainment use.  However I expect that what I show here will be more likely to get overlooked (and therefore "passed") during an inspection than the cable that most small sound providers are using, but if you use the following information as a guide for your own gear, you do so at your own risk.

Neutrik PowerCon connectors are wonderful things.  I use them where ever possible.  Their advantages include:  They are rated for 20 amps.  They lock positively (unlike Edisons, and Hubbell or other Twist-LocksŪ).  They are reasonably priced (unlike most Twist-LocksŪ, especially chassis mounts).  The male connectors do not protrude from the housing like Twist-LocksŪ and as such cannot be bent.  They mount in the same size panel hole as Neutrik NL4 loudspeaker connectors and Neutrik D series XLR connectors.

Two minor caveats: They are not male and female as with Edisons and Twist-LocksŪ, so to connect two cables together (to make a longer one) you need a pricey coupler.  The largest cable that they will take is 10-3 type SJ or 12-3 SO (both of which are heavier gauge cable than many small sound companies use).
(See the warning above about SJ and SO)

NAC3MM Cable Coupler.

Left: Mains feeder cord.  The Edison is a Pass & Seymour 5266-X, chosen because it's robust, accepts large cable, and is cheap (about $8.00 at Menard's).  Right: Mains jumper cord.  Center: Stringer box ("Band Power Box").  The cable is Coleman 10-3 SUEOOW Seoprene 105 (from Menard's - also check CamelTraders).  I have various lengths of both kinds.  All racks and band power boxes have a PowerCon Inlet and Outlet ("Thru").  Any feeder cord can feed any rack or band power box.  Any jumper cord can jump from any rack or band power box to any rack or band power box.  This allows for any contingency:  If the venue has plenty of wall outlets, every rack can have its own feed and the stage can have one or two;  If there is only one outlet, I can daisy chain everything (up to five band power boxes, two amp racks, and two FOH racks plus the console, and the only connection(s) that can possibly be pulled, kicked, or vibrated apart are those where an Edison plugs into the wall.   (The breaker may blow, but hey...)

The Band Power Boxes were $6 each at Home Depot.  I removed the power cord and installed the PowerCons.  The PowerCons are wired straight through - the switch/breaker effects only the outlets on the box.  With a hand-full of boxes and jumpers, one can daisy-chain outlet boxes anywhere on stage without worrying about something in the chain coming unplugged.  (Unfortunately, this box is no longer available from Leviton, in spite of what Leviton's on-line catalog says.  However a version with surge suppression is available as the Tripp-Lite model TLP808.)  (You have to remove the surge suppression components in order to install the PowerCons .  This is ok, because what the suppression components are best at is setting the plastic box on fire when they fail.)  Do a Google search to see who has the best price.   (The Tripp UL800CB-15 is an all metal strip.  However to use it will require removing the power cord and blanking the hole, removing the switch that is in the way and blanking the hole, and likely removing one duplex and blanking the holes.  A lot of extra work.)  (Or use my original design.)

Update: I've been using these for several years now, and I've not been gentle with them (although I don't think any have been stepped on or had a case rolled over them).  The only problem I've had was when some jughead removed a PowerCon without bothering to release the locking tab.  (Which took a lot of effort!  I had to replace the PowerCon, as it would no longer lock.  Bloody musicians!)