I'm using one of those cheap 7ft. folding tables I got from Staples for about $40 on sale... I've been using it for about 8 years now.
It's ugly, but it easily fits two computers with tons of room, and they're deep.
(Even though I've upgraded to flat screens, it's still great having depth. )
I will say that my 4 year old son (at the time) jumped directly on the middle of it a couple years back, and it has the slightest bow down the middle. If you keep your kids from diving onto it, you will have no problems.