I bought the Charlie's Soap online, direct from Charlie's. It's lasting a long time -- at only a Tablespoon per load, I guess it would!

As for detergent vs. soap -- I've found a number of references that claim they're different, including the "how to launder wool" article that was linked in the woolweenie thread.

This stuff is great. They advise you to run a load of just water and Charlie's through your washer first, to wash out the residue from all the other stuff you've used.