I'm a very keen juggler - I'd love to know if there are any points of reference to make juggling entertaining rather than just 'look at me' type stuff, which, at the end of the day, circus skills are.
I once saw a magician use juggling in his act; he juggled five balls, and got a small child (about 7 years old) to hold an absolutely massive net to catch one ball at a time as the mage lobbed one towards him - it was so funny as the guy juggling would throw one the wrong way and blame the little boy for moving - there was loads of funny business like that.
The only other truly 'interactive' juggling I've seen was '
The Pretentious Juggler.' He would ask a man in the audience to throw him his three juggling knives whilst he was on a Giraffe (6ft) unicycle (the juggler on the unicycle, not the spectator!). He would also have a child help him with his hat manipulation and juggling - and get the audience to clap every time one of his hats was on his head. Loads of business available there too. Very funny. But not a magician.
The only thoughts I've had for juggling as well as magic is vanishes and appearances with the items to juggle with - maybe produce three juggling balls at the end of a cups and balls routine.