If you're looking for a very good flash game to use that idle time with, then I would highly recommend Rebuild--an awesome new turn-based strategy game.
Unlike the hundreds of other games with zombie enemies, Rebuild puts a very clever twist into their plot. Don't expect to tot some guns and blow the heads of the brain-eating vermins, instead, you will be exercising your mind at planning, and planning carefully.
The game is set in a randomly generated town that has been infested by zombies. You and few other survivors have built a fort as a refuge, but if you were to survive for long in this set-up, you would have to reclaim the city block after block, ridding it of zombies and recruiting any other survivors you find inside buildings and other infrastructures along the way.
In these dire times, you can send your men on a mission to scavenge for food, just make sure he is accompanied by a soldier lest he would be devoured by the undead. You must also deploy a squad of your soldiers and clear the building of zombies and later on have it repaired and reclaimed by workers. Reclaim a laboratory building and make your scientists do some research...it's not too late to develop new technologies against the hordes of zombies, after all. And watch out for the morale of your men--if your fort is too cramped up with many hungry people, you would have to reclaim apartments to house them and farms to keep a steady supply of turnips and corn cobs. If you don't do so, your men will turn up dead from hunger or simply refuse to work. From time to time, random characters will knock at your door and volunteer to be part of your force so be sure to have vacant rooms for them to stay at.
Also, make sure to garrison the police stations and other vital installations to put up a stronghold.
If you think you can just send out as many scouts as you want to explore the streets in the hope of finding food and recruits, well you better plan it out carefully and make sure you have enough force to defend your fort as armies of zombies attack at nightfall.
Overall, it took me 5 straight hours to reclaim the entire city on a normal difficulty level, and many soldiers and civilians were martyred during that entire period. But there is nothing sweeter than sending the zombies back to their graves.
