The folks at Machinima released a short film about the world of Half-Life this morning, and while it may be cheesy...so is the series. The positive is it has a lot of action and references to the series that fans of the game will really appreciate! Here's a description from the creators...

May 16,2003: When Gordon Freeman inserted the sample GG-3883 into the Anti-Mass Spectrometer, it was the beginning of an unstoppable chain reaction.
First the Xen Aliens invaded the Black Mesa Research Facility; Then the US Marines were call in to contain and eliminate all threat.
After the complete failure of their operation, the CIA black operatives were send to arm a thermonuclear bomb in order to destroy the entire Black Mesa facility...
Follow USMC private Cooper through his journey in hell.

It's not perfect, but it's as close as we are going to get to a Half-Life movie anytime soon!