Black Mesa -- the remake of the original and famous Half-Life -- was finally released recently. If you want more Half-Life goodness in your life, Black Mesa: Uplink is here as a supplement to the remake content, recreating the original Half-Life: Uplink demo, with fancy new graphics and all the other bells and whistles.
As you may recall, Uplink featured content cut from the full game, so Uplink plays like a standalone "episode", if you will. It's short, but worth your while, especially if you're a hardcore Half-Life fan.
Hit the source to download. Note you'll need Black Mesa installed, too.