One of the main ways I confirm whether a league is active is via their activity on social media, primarily Facebook. If it was feasible, I would contact every league and have them confirm that they are active. That would be a full-time job by itself. I already have a full-time job, and a life that partially revolves around derby, so I have to find other ways to keep tabs on leagues.
The best way I've found is to go where the leagues are. Right now, that place happens to be Facebook. Yes, some leagues have their own websites. And some leagues use Twitter. There are even some leagues that have a Tumblr. Heck, if you dig deep enough you can find leagues with a MySpace account. But Facebook appears to have become the standard place forread more Facebook Twitter Google+