I noticed there's some new badges as from today.
From the name of those badges, I inferred there is some new features to put a bounty on someone else question.
Is there any place where those changes are announced? (and the new badges listed?)
Announcements of new features tend to happen in the Stack Overflow blog, though if you don't follow it regularly (like me) you can miss them.
The other thing to do is check for questions that have been recently tagged status-completed here on Meta. This often precedes the blog post.
Additionally if you hang out on Meta you might see questions being posed by Jeff and the other diamond mods that indicate that something is in the offing. See here and here for questions that revealed the bounty badges and the newly added information about which post was responsible for which badge.
ripper234 covers the bounty system change. The bounty badges have not yet been officially announced outside of the original discussion for implementation and some scattered [status-completed] tags.
In addition, it's easy to miss but there's also a new Copy Editor badge for 600 edits. It was announced over in this question.