Hi Nicole,
Cathe is definitely the best, but there are a few other DVD:s I use for a change of pace. I should add that I haven't really found ones that compare in intensity to Cathe, but just for variation here's what I do:
Gin Miller's Intense moves for an interval workout (not quite as intense as the imaxes in my opinion, plus it's a little bit shorter. I love Gin though,she's great!)
Kari Anderson's Hot Steps for low-impact step, pretty dancy. I also like Kari's Angles, Lines and Curves II (not for developing muscles, but nice for something different).
Christi TAylor for some dancier step and fun hi-lo (I got the hi-lo heaven etc. 4 workout compilation DVD). Not as intense as Cathe, but gets pretty close. Also, if you like more choreographed stuff, it's great! Time flies by doing it.
Charelene Prickett's Crazy for Step. Pretty low-impact, steady-state step routine that keeps the heartrate up pretty good. Production isn't anything fancy, but a fun basic step workout.
Top of that it's mostly Cathe...

) nice to hear what others do, though,
enjoy your week,
Maria