Nice contraption for early muscle-ups
 

http://journal.crossfit.com/2010/04/leo-muscle-up.tpl

Halfway through, there's this rig-up with a squat stand and bands.

i just realized that it's in the CFJ so you may not be able to see it

It's interesting and novel because one of the issues is once the band helps assist you into the lower portion of the muscle-up, the dip- there isn't enough tension in the band anymore to help you with the dip.

I'll let someone else describe it because Leo posts here I think and it is his article and IP.

i tried setting up bands that way for cross work the past 2 days. i like it a lot more than looping it around a pullup bar and wrapping it around my feet. you can get on it then unhook it and hook it back in so fast. i've also tried it by setting it lower and putting my feet on it as i planche on the floor. i've also had it assist v-ups in a similar way. i'll try it with front levers next time.