Haven't been on here in awhile but thought I would post today's lunch break shopping in case it's of general use.
For Americans, calhouncycle.com is running a flat rate $2 winter shipping sale and offers a small discount to Schwalbe MSRP. Lots of small wheel tubes here: Tires & Tubes - Calhoun Cycle
(Also the Airnimal on their sale page is pretty sexy.)
If you have a large order or live in Europe, sjscycles.co.uk has marked down a lot of their Schwalbe stock: Inner Tubes products from SJS Cycles
15 quid shipping to the US, 3.50 to UK.
I know some people think there's no such thing as too many patches, but part of the motivation for me was that I wanted to get the exact right size and a few spares.