The best skippers I've seen are Mayweather and Duran. Roy Jones was pretty decent in his day. They have videos on youtube.
I've been told that as any 10 minute cardio exercise skipping is the best. I wasn't sure.
I got this from my book, which it says is the standard measurement for all exercise ratios, in case it's a useful comparison for skipping versus other activities. PN could probably give more insight than I.
Badminton
.044
Basketball
.063
Bicycling at 5.5 mph
.029
Bicycling at 9.5 mph
.045
Climbing hills with no load
.055
Climbing hills with 9 lb. load
.058
Climbing hills with 22 lb. load
.064
Cooking
.022
Dancing, ballroom
.023
Dancing - Aerobic, medium pace
.046
Dance - Aerobic, intense
.061
Golf
.038
Grocery shopping
.028
Jumping Rope at 70 jumps per minute
.074
Jumping Rope at 125 jumps per minute
.080
Jumping Rope at 145 jumps per minute
.089
Mowing the lawn
.051
Racquetball
.081
Raking leaves
.025
Running at 6-minute mile
.115
Running at 8-minute mile
.095
Running at 9-minute mile
.087
Sitting Still
.009
Skiing cross-country - walking
.065
Skiing cross-country - uphill
.125
Snowshoeing - soft snow (doesn't mention hard snow

)
.075
Squats
.096
Swimming - crawl, slow pace
.058
Swimming - crawl, fast pace
.071
Swimming - breast stroke, fast pace
.074
Table tennis
.031
Walking - normal pace on asphalt road
.036
Walking - normal pace on fields & hills
.037
Weeding
.033
Weight training - free weights
.039
Weight training - circuit training
.042
Volleyball
.023