Well now that I've got a bit of time on my hands, I must say that (as a schoolboy wargamer and former comp games publisher) I've gotten in to World of Tanks (yes sad I know).
It's really superb, online interactive game using historical(ish) vehicles, it's totally free (unless you want to progress quicker) and you get the chance to form platoons and clans with friends for a bit of world domination....
Have a looksie here..
Soon they'll be releasing similar products using aircraft and battleships, so something for everyone, if you're of that ilk...
If you fancy having a go - get stuck in, it's vast to start with, but you soon get the hang of it..
Let me know if you have a go, and if you have any questions..
(health warning: beware it's very addictive... )