The obligatory link: Dig Your Own Grave - Cubefield
Cubefield - A simple enough game, really. Guide your "ship", and I use that term loosely, with the left and right arrow keys through fields of blocks. If you crash, it's game over... and you keep playing until you crash. The early portion isn't terribly difficult.
High scores are available on the site, though if you want something to shoot for right off, I racked up 329k on my first play through.