Well, there's one main one that is happening today. And that is the moon. What about it, you ask? Well, simply put, the moon is going to be bigger than normal.
According to PopSci, the moon will not only reach its closest point to Earth for all of 2013, but it will also be a full moon, making it the biggest full moon of the year. People are calling it the "Supermoon." But here's an interesting fact: whenever the moon is this close to the Earth, the changes between tides become greater. That means a lower low tide and a higher high tide. Some unsuspecting ships may become victims of the larger low tide much like what happened two years ago.
But I honestly could care less about that. What I'm looking forward to this year (astronomy-wise) is the comet ISON. It supposedly may become the "comet of the century" after it orbits close to the sun. Its tail may light up the night sky in a spectacular fashion.
That's coming later this year, and it's zenith should be around November 28th of this year.
So grab some binoculares and dust off that telescope. This year, the sky is going to be amazing.