The Unknown Language Round format is becoming popular outside of Codeforces: Chaos. There are only 6 problems, which is less than an ULR typically has, and the problems themselves are easier, but that's a good start.
P.S. I know it's too late for a contest announcement but I had no time earlier - I even got late for the contest itself.
P.P.S. My report of the contest participation: Chaos Chef.