Ah finally something I know I'm good at! Well, competent at least... Depends on what you're after.
If you want HIIT I use a 20 min. session starting with 100 double unders and finishing out the first 5 min. with a combination of high knees runners, alternating sets of one foots (10x10), feet-only jumping jacks, and side to sides. Start the next 5 min. with another 100 double unders followed with the same. Repeat. Then on the last set, leave enough time for a final set of 100 double unders.
I've also used the jump rope between sets during weight training.
I've also used a 10 min version of the HIIT session as a morning metabolism booster/wake up call.
As I've mentioned on the board here before, wear long sleeves while learning the double under. Welts on your arms from the missed jumps hurt like hell.