2 of 2 Added link to Mr. Beer fermenter

What's a good small-batch fermentation vessel?

After getting started with a few kits, I'd like to start experimenting a little bit. I'd like to start off with 1-gallon batches on anything I'm not sure about, though. I have a growler that I'm considering trying to fit an airlock into, and I've also seen some people mention using the 2-gallon fermenter from the Mr. Beer kit for small batches. Are there any other good options?

EDIT: You can buy the fermenter that comes with the Mr. Beer kit by itself for $15 (but it's on sale for $10 at the moment). Very tempting: http://www.mrbeer.com/product-exec/product_id/377