Yes, I adore Splenda!! Starbucks was actually
out of Splenda today so I had to resort to putting
Sweet-n-Low in my latte -- blegh!
And building on the idea of using extracts, another zero-calorie flavoring you might try, if you have a favorite flavor, is Torani sugar-free syrup. That's the kind of flavor syrup they use in Starbucks and other coffee houses. I have both Raspberry and Vanilla, sugar free of course! I also found that they do sell smaller bottles than those you typically see in a Starbucks, so that's the size I bought.
And oh, I almost forgot, regarding the many types of extracts, I first looked for ideas in the grocery store, of course, then I did an internet search and found about a kajillion types. I actually ordered a bunch from Amazon.