It’s surprising that Jeep designers didn’t incorporate this to start with. It’s a potentially hazardous design flaw. That tailgate is pretty heavy – especially with a big tire on it, yet if you park anywhere there is a bit of a slope, the door can come swinging closed on you. Anyway, some clever folks on the jk-forum have put together a simple mod to the door, by adding a gas shock to it.  They had part numbers and everything, but some of the companies don’t ship to Canada (free trade failure, or ‘merican attitude?).  Here’s a link to one of the variations that got posted.
I found a company in Saskatoon, called LSTechnologies (LST) that sells the parts needed.  They were very helpful in matching up a few of the parts I was after:
* B8-210-505-190N Gas Spring
* T1GPB-145 Angle Bracket 10mm Ball
* T1BKT-04 Angle Bracket
Some additional parts/materials that I’ll be using include:
* mounting bolts
* metal bar to help strengthen the mounting point on the tailgate
* rivet nuts? Still trying to determine exactly how I’ll attach the mounting brackets to the vehicle
Looking forward to receiving the parts from LST in the next few days… I’ll try and add some photos of the install.
UPDATE — Oct 27, 2008 I’m shocked!…(sorry, no pun intended).  The new shock and mounting brackets arrived today! I just ordered them Friday afternoon.  Kudo’s to LST and Canada Post for amazingly fast delivery.  Everything was packed exceptionally well.  Just need to pick up some stainless steel bolts, and some metal to reinforce the tailgate.