The five planets we can see with our naked eyes (assuming you don't live in a bright city like I do) will be in the same part of the sky at the same time. This display will be easy to spot in most parts of the world, but it's not an alignment. It's a less glamourous and omnious clump.
Mercury,Venus, Mars, and Saturn will start converging in the same region of the sky on April 20th, and will be closest (within a span of 10 degrees) on May 4th. Jupiter will be a bit higher away.
Doomsday predictions, begin!