When evaluating new platforms and frameworks it helps to know how active the developer community is and how much it's growing.
I've created a query page here that shows technology activity over time at Stack Overflow:
For example when comparing Javascript frameworks we can see that knockout.js has a bigger community, but angular.js is growing more quickly.
The mass is the total number of posts and the momentum is a weighted average of growth over the last six months.
Mass and momentum are key factors to knowing which developer trends will turn into decisive shifts.