Do you like cake? I've discovered recipes that you use low-cal (or regular) cake mix (yes, it comes in chocolate!) stirred up with 12 ounces (1 can) of diet soda. That's it. Nothing else. No eggs or oil. Couldn't be easier. Turns out great!
With chocolate cake, a can of diet cola (Cherry Coke!) or Dr. Pepper.
Yellow cake with 7-Up, other citrus, Orange Crush is great! I've been wanting to try Fresca, if it comes in diet.
White cake and Big Red or peach, spice cake and ginger ale. Add some nuts or fruit, raisins, etc.
For icing, use sugar free Cool Whip, maybe mixed with sugar free or fat free pudding.
I think the Weight Watchers web site has some more suggestions.
Happy baking.