Although I think that seeing which monks have advanced in level recently may be somewhat interesting, I think it would be more interesting to see which monks have gotten the most XP in the last few days. That is, which monks are the most active and are posting the best nodes in a given time period - the last week, for example.

This might be a good way to provide an incentive (e.g., a monk on this list for seven consecutive days gets a cookie - or more XP).