Here's my little trick: (stole this from this board so whoever originally posted it may feel free to claim it )

2 packets Knox unflavored gelatin
1 packet of Kool-aid flavoring (no sugar or aspartame added, just flavor)
8-10 packets (16-20 teaspoons granulated) Splenda to taste
The water the recipe calls for (I think one cup hot water, one cup cold)

Follow the amounts listed on the box (there should be a basic gelatin recipe) and this makes splendid splenda jell-o.

Plus you can use a variety of flavors due to the amount of kool-aid flavors.