Valve have kept quiet on the subject of Half-Life for a number of years now, but every once in a while some new information leaks out. This time it's 32 images with artwork that seem to come from 2008 (so a lot could have happened since) - and we're still not sure whether Episode 3 will ever make it out - or if it is getting reshaped into Half-Life 3...
Anyway, you can have a look at all the images over here. Regardless of where Half-Life may be headed it's an interesting piece of history.