There still might be a free version of True20 at http://true20.com
That could more easily explain True 20 and do it faster. Bottom line: the D20 is the ONLY die used in that game.
I've been fancying something like this for a long time and wanted to create a d20 system in which 0 was the norm with positive or negative modifeiers etc, now I've found out that it's already been done, I'll have a good read.
I've tried a couple of True20 games in the last month, basically a home-brewed Traveller/Cthulhu crossover. The reception was good enough to agree to have another go at it, perhaps a more original backdrop next time.
The mechanics are fast and simple, less crunch than both D20 or T20 and the emphasis is on narrative. It suits some games though I think I'll stick to practicing with T20.