Most of us are likely involved with java in some way. Kotlin has received quite a bit of buzz lately as a saner-than-scala next-gen jvm language. I count myself as one of those anxiously awaiting it's 1.0 release.
As you can see it's still in development, so it can't be as popular as it can be when released final.
Kotlin and Ceylon are the two new JVM Languages that have a lot of potential and I hope will be pretty popular :) The first is developed by JetBrains and the latter from JBoss, so they have good people working on them.