I think farmingforum is very nice, Don. Not just for 'real' farmers but for those who are moving into small farms from city dwellings, and need a lot of advice. They would be used to getting this on forums and so on. I'm guessing that 'farming' is a much better keywords than any of the others in your forum names. Would this be the right way to judge a forum name? As you know from my own earlier thread, I have a personal interest in this aspect.
I would also more naturally say 'martial arts' than 'martial art,' and feel that the singular version is not specific enough for any one particular martial art (type of karate, judo, whatever). I note that Patrick O'Keefe, writer of
Managing Online Forums, says that he runs a karate forum. Interestingly, he suggests the word to go with the keyword should be 'forums,' although Google's keyword tool definitely seems to prefer the singular, which I think is correct too (the plural of forum properly being fora, but anyway the plural seeming to suggest something much broader than a single site with many threads. Even think of this forum as an example of a large site, I think 'dnforums' would have an odd ring about it.
Sorry for going on so long, but while I don't consider myself competent to offer a valuation (surprise!) I have plenty of opinions to offer.