I keep my "using" dice in a multi-compartment plastic box. I can separate them somewhat and choose dice easily. I believe the box was originally designed as a parts display for conventions. My older dice are in a large leather bag.
I have a hand-made bag my wife made me fifteen years ago. It contains my green set, and my oversized set for when my condition acts up badly enough that I can't pick up the small ones. She has a leather bag she got as a gift from a spoiled rich friend of ours (we were on public assistance and disability at the time) who was unable to speak when she breathed in, and a new leather bag with an Isis logo on it which I bought her from the Gamer's Bag. Both my sons got Skullbags, the 18-year-old got the faux leather, the 13-year-old got the canvas, and we split the pound of dice between them to augment their one set each. We keep a mason jar of spare D6s for if we ever play anything but D20 again (unlikely).
Old dice.. Hm. Mostly, we throw them out when they get worn and get a new complete set.
My father works for Philip Morris in the tobacco division. He has been collecting company oddities for many years now. One of the oddities is a metal tin replica of a pack of cigarettes. He had eleven, but he let me have one. I opened it form its packaging and found and was just long and wide enough to contain one set of dice. So I keep my lucky set of dice in there and take it with me evry time I go gaming (outside of the house that is).
I have a good-sized wooden box that I keep them in. They live on the coffee table, so whenever someone needs some dice they reach in and grab a massive handful.
As an aside, in my epic game I ruthlessly mock anyone who doesn't roll all their dice at once. One pc rolled 40d6 lingering damage last night- all at once! Good times, unless you happen to be the npc suffering that 40d6...
In addition to a "traveling pouch" of a standard polyhedral dice set, I keep most of my dice in a plastic tacklebox, sorted by type. I also have several funky dice (30- and 100-sided, skull pips, weather effects, treasure types, superhero icons, etc.) that I keep in one of those compartments.
Oh my! I'm glad I stopped back into this thread. I guess I misunderstood the question and posted without reading other posts. That'll teach me!
I have a very nice dice bag from "The Gamer's Bag" that was gifted to me by my friend Barendd Nobeard in honor of last GM's Day (March Fo(u)rth for GM's Day!)
Besides which, if I was going through customs I would most certainly hire a dice mule...