The popular tags page http://stackoverflow.com/tags?tab=popularhttps://stackoverflow.com/tags?tab=popular lists tags ordered by number of questions asked.
The page also displays in most cases how many times it was asked today and this week. I noticed that many of tags have a much higher "questions per week" than tags above it.
To me this signals that the tag is currently hot. For example if you reorder the top 55 tags by week and compared this week rank to the overall rank and only included tags that had a difference of greater than 5 you would come up with this list currently.
Tag Overall rank Week Rank Difference
-------------------- ------------- --------- ----------
android 9 3 6
objective-c 15 9 6
ios 32 18 14
ruby-on-rails-3 53 21 32
xcode 40 25 15
visual-studio-2010 54 34 20
json 52 38 14
web-services 47 41 6
pearl 51 46 5
I find this information very interesting.
As an alternative the tags page could just be sorted by questions per week. Since it clear that this data is already being used I would be surprised if this had a perf impact on the database.
