I’m not going to claim you’ll be playing any of these games for months and months on end. Likely you will get bored with either of them in a month or three. But in the meantime they’re free, they’re fun, and you can play either of them from anywhere you’ve got a browser available. Perhaps most importantly neither one involves any big time commitment. They can easily be picked up and started but the total time needed to play either one is literally just a few minutes per day.
This is a fun game that gained a lot of popularity in a hurry a few months back. In it you play a single human or zombie character. There has been an outbreak of some disease that causes zombies (see Sean of the Dead or 28 Days Later for details) and the humans are in a fight for survival against zombies looking to turn all the living humans into shambling zombies.
There is no “death” in the game as you turn into a zombie if you are a human character and you take enough damage to die. Even if you are a zombie though, there’s always the chance you can be re-vivified by some technology available to some of the human characters. A fun game with exploration, skills to acquire, combat, equipment (when you are human), and no real reason to quit until you get bored. Total time to play all your moves per day is no more than 10 minutes.
I’m still playing this one myself. If you are already a big game player I can probably best liken it to a real-time strategy game (RTS) like Warcraft, Starcraft, or Age of Empires. Except that it is browser based so there are graphics but no animations. You don’t get to watch a little person walk over and build your new structure but after a certain amount of time has elapsed off the clock, the construction will finish in exactly the same way. So it’s like the standard RTS experience, just distilled a little bit.
The total time to play this one is greater than Urban Dead. I don’t think there is any way you could possibly play it for ten minutes a day and get very far. But it’s still probably not more than 30 minutes total and you can spread it throughout the day with just a minute or two here and there.
There are a few sites that have information on web based games like Travian and Urban Dead. My personal favorite is MPOGD. That stands for Multi-player Online Games Directory. They discuss popular online massively multi-player games like Everquest and World of Warcraft as well as smaller entries like the ones I just mentioned. Go through their Game of the Month winners for a who’s who of fun games with all kinds of themes, many of which can be played at no cost.