The Logitech PlayGear Share Audio Splitter is a small device used to split one audio output into two.
The product was designed for the PSP, but as it uses standard 1/8" audio jacks it will work on any device that supports them, such as any computer, and will output just fine to any set of earbuds or headphones. It's about 3" long and fairly flexible, so it works well even in cramped spaces if you need it to. The material goes back to its original shape though, so if you want it to stick in a permanent location you're going to need some tape or glue.
The sound isn't degraded when you split it, so it can be used comfortably as both a temporary and permanent solution if you need to split your audio output. Although originally designed for portable devices, the Logitech PlayGear Share can also be an inexpensive solution to having speakers and headphones attached to your computer all the time.