If you're a fan of the Half-Life series like me, you'll wanna read the excellent web comic Concerned by Christopher C. Livingston. It's the story of the journey of Gordon Frohman, former employee of Black Mesa and now simple citizen of City 17. This journey will lead him to the Citadel following the exact same path as Gordon Freeman, but not for the same reasons... Be advised that it's better to know the game and its universe to fully appreciate the humor of this comic.

I also encourage you to watch the machinima series Freeman's Mind, by Ross Scott. The man plays the game from end to end, commenting as if he was Gordon Freeman. As previously said, you may prefer to play the game before watching this to really enjoy it. You may also want to skip some lenghty parts, but the overall thing is very funny.