I actually just did this for myself because I want to use my tower more before the new workouts come out. Most of them are bonus sections, not full workouts. Some others in addition to the ones mentioned above: XTrain Legs has a bonus barre section, as does Lean Legs and Abs, and Great Glutes has a chair section.
There are also a number of Cathe Live workouts with a barre section. None of them are very long, about 10-15 minutes as part of a lower body workout usually.
One other thing I tried that I liked was doing all of the lower body sections from the DVDs that came with the Fit Tower. Doing the three short leg workouts back to back made it just a bit more challenging. You could probably do the same with all of the upper body and core sections as well.