Wow: I feel like having lived under a stone for 8 years, as RosettaCode has been alive since it was founded in 2007 by Mike Mol.
The idea is that you solve a task and learn from that, or learn by seeing how others have solved tasks or draft tasks.
So in a sense it is similar to the Rosetta stone: it has different languages phrasing the same tasks.
There are already a whole bunch of languages on RosettaCode (of which a few are in the categories below), and you can even suggest or add your own languages.
When you want to solve tasks, be sure to look at the list unimplemented tasks by language that leads to automatic reports by language (for instance two of the languages I use most often: C# and Delphi).
I’m sure there are lots of programming chrestomathy sites, even beyond the ones, and it feels very similar to programming kata sites.
–jeroen
The Wiert Corner - irregular stream of stuff 