For awhile, I've been wanting something that would carry an overnight's worth of gear when I go on a motorcycle adventure. (When I go longer than that, the saddlebags come out, but they're overkill if I'm just making an overnight run a couple hundred miles away, and staying in a motel instead of camping.)
After considerable noodlin' of the situation, I settled on the Aerostich Dispatch Bag.
Aerostich, out of Duluth, MN, makes some awesome motorcycle gear including the Roadcrafter zip-in suit, as used by SERIOUS touring motorcyclists. Their catalog is always chock-full of interesting gear; I've ordered some nice stuff from them over the years including some elkskin "roper gloves" that are fantastic. Their website is here.
I got the bag in the hi-viz yellow. It has a large reflective panel as well, making it about as visible as it can be, without disco strobe lights. The Dispatch is the smallest of 3 bags; the base is 12 inches across and the top 18 inches. (Volume is 1100 cubic inches; the bigger "Courier" holds 1700CI, and the biggest "Parcel" holds 2700CI - a regular back-mounted duffel bag! I was willing to sacrifice some hauling space in exchange for long-term comfort, since I'll be using different luggage when more volume is needed.
The Dispatch should carry my netbook computer, rain gear, some provisions and toiletries quite nicely.) I expect this will be a good option for (bi)cycling, as well - an alternative to a briefcase or backpack. I expect I'll continue using my fanny pack for my sack lunch and a couple small items, but the Aerostich bag would be nice when I need to haul some clothes or whatever.
It's expensive at $77 - but build quality is excellent (made in the USA, too!), and after comparing with some other brands, that was right in the ballpark for quality gear. Hopefully after a summer's worth of use, I can post some follow-up impressions.