GK Glossary (http://interestingdiscussions.blogspot.com/2008/07/generation-kill-glossary.html) - you probably shouldn't rely TOO heavily on this the first time around, otherwise you will be pausing every other second, heh. It's best used w/ multiple viewings; it's more more fun to learn incrementally imo. :)

This site (http://featuresblogs.chicagotribune.com/entertainment_tv/2008/07/generation-kill.html) breaks down the platoon nicely. You don't have to read everything, however I think the Chain of Command chart and the Humvee rosters are really helpful (Humvee #1 is the main POV for the series)