BKB readers know I'm a little obsessive about oral hygiene:  I've written about the best toothbrush, the best floss, and one of the three different kinds of mouthwash I use.  Okay, maybe more than a little obsessive.  But I'm also really environmentally conscious, so I think long and hard about using or recommending any disposable item.  Years ago, I bought a supply of SmileSaver disposable toothbrushes.  They're pre-loaded with paste in the handle — simply push the handle in to dispense the paste onto the bristles, and brush as usual.  But you still need water, and a place to rinse and spit, and they're not that much more convenient than carrying a travel-sized toothbrush and paste.  The Colgate Wisp is different.  Instead of paste, it uses a mouthwash-like "freshness bead" which releases a small amount of liquid into your mouth as you brush.  You don't need water, and you don't need to spit out the liquid, so it's useful in places where getting to a bathroom is inconvenient. It's also really small at 3.5", which is a little unwieldy, but eminently packable, and has a soft pic at the handle end for cleaning between teeth.  Find them at your local drugstore, or buy a pack of 16 for $8.49 from Drugstore.com.