"Nesting Kits" are big in drums right now, as popularized by Yamaha's
Hip Gig http://www.drumcentral.com/drumsetpics90.htm
The whole kit, shells, hardware, eveything, packs into #1 the bass drum, which unhinges on one end to become a big "suitcase" and #2 the same-sized cannister-style throne.
Personally, I need bigger shells, but the idea is still a cool one. I just got a rolling hardcase for golf clubs, which I can pack all of my gigging hardware into. This portability and convenience thing becomes a real priority once you reach a certain point in your musical maturity (and don't have roadies.)
Historical sidenote: 20" bass drums became "traditional" in a jazz kit because they fit in the trunk of a New York City cab!