Sorry if this was already announced here, but two great events are at hand and probably some users are still unaware:

Google Code Jam 2014 — Qualification round starts on April 11 and is 27 hours long so people from any timezone can participate.

TopCoder Open 2014 / Algorithm — initial rounds are taking place on 5-th, 12-th and 26-th of April.

TopCoder Open 2014 / Marathon — first round starts on 9-th of April.