I've been using the iPod another way lately, and it seems to be working out well. Two sets of commercially available CDs, the Penton VocabuLearn series and the Instant Immersion sets, have segments of five to fifteen minutes of single-rep vocabulary and phrases. (Unlike the Pimsleur method, which asks "How do you say X in the target language?", pauses for your reply, and then gives the proper reply with time for repetition, the single-rep approach gives a phrase in either target or source language, with a pause for translation, before giving the correct reply once or sometimes twice.) Single-rep audio materials are hard to pick up a single hearing, but cover a lot more ground per half-hour than a Pimsleur lesson does.
So, I made an iPod playlist with Chinese and Japanese single-rep material, and various music CDs I had made for the target languages, and shuffled them. This is good background material while working... I can shift my attention to foreground tasks and back to the audio as appropriate, and don't have to worry about missing sequential material. The goal is just to take advantage of what I can, during the pauses during daily work when my attention is not fully required, and it doesn't matter if I repeat some of this material, or never get some of it. It's a way to squeeze a little more vocabulary work into the day without affecting my main work.
The "spinning plates"? There are many things I'm trying to learn right now, and it will take awhile to get through my full agenda. I don't see myself being able to make equal progress in each area each day. But some breakthrough work will require intensive short-term attention, as my learning of Devanagari script this week requires, or the ability to get a significant way through a single textbook. The tactic is to take these short bursts as appropriate, but to keep the momentum going on the other skills I'm trying to simultaneously learn... just like a juggler, I need to watch each of the plates, making sure each one has enough momentum to keep spinning, and to add new plates in the holes, as their momentum permits. I won't be able to do everything each day, but I want to keep a forward momentum in each area.