I think a lot of the program is hands on, so I'm not sure how an on-line version would work. Also, there's a big component that involves volunteer work - community gardens, soil testing, taking gardening questions by phone, etc, which would all take a fair amount of time. As I understand it, this work is an ongoing commitment, and you lose the "degree" if you don't continue to do the work.

Why do you want this certification? Do you want to BE a master gardener and participate in the volunteer program? I'm asking because I'd be interested in the training but don't really have time to do the volunteer part.

Maybe your county extension agent could help you locate an evenings/weekend program?

Here is a link that might be useful: wikipedia master gardener page

I would love to hook up on the volunteer side.My knowledge base is pretty good. I had several MG's and interns volunteer at my sale and they all agreed I was as knowledgeable as them. The main thing the class teaches as I understand is HOW to find the right answers. not memorizing them.
I just can not give up 16 weeks and 500 bucks to drive 4 hours round trip to get a certificate that validates 90% of what I all ready know.I'd do it for 500 buck at home in my jammies on MY time and then volunteer,
Being an MG will help my plant sale by getting more MG help for it allow me to hit the speaking circuit and raise the profile of it.

And last but not least being an MG intern a MG mentor works with me..and I'd steer as much of the volunteer requirement to my plant sale as possible. Killing 2 birds with one stone.