There's a gal who makes mustard for sale at the local market. We've chatted a few times, and I even volunteered to help make a batch, but so far she's not taken me up on it.
Mary pointed out that a (somewhat) recent edition of Sunset Magazine had some recipes for mustard. They looked pretty easy and fun. Mary even bought some mustard seeds and powder from the bulk bins at the co-op, so I had no excuse not to try them.
Simone and I mixed up 3 different batches. Two have to soak for at least another day to let the seeds hydrate, but the other was made from powder/ground seeds and just sat for a few hours - at which point I finished it up. It is the Hot and Tangy Mustard Recipe, and I think it's pretty good. It's got the heat of Chinese mustard, but is definitely more complex - like a cross between Chinese and dijon.
The next thing is to figure out how to use 3.5 cups of mustard...