by number of articles
by edits per article
by starting time
Hebrew is rated fairly mediocre by number of articles (19-th place with ~43,800). On other hand we have a pretty good rates of edits-per-article and articles-per-total-pages-number and our Wiki started relatively late at July 2003. Thus the community seems to be strong and Hebrew Wiki shows a good prospect.
Polish Wiki have an unusually high number of articles and good traffic rate, but other ratings are lower.
Russian and Spanish show less progress than I expected.
And Arabic is just where I expected it to be - at 34-th place. I suppose all these princes with their cars, falcons and rifles don't have time to use computers. No single rich guy to pay pitiful $50,000 or so for transfer of a printed encyclopedia into Wiki engine just to save a face. Bah.