Apple has launched a new "Try Before You Buy" section in the App Store, and while it's a poor excuse for an "official" demo system (it's basically just a collection of free apps with full versions to purchase later), there is some good stuff to find in there, like this one.
Today we're passing on the casual games for something a little deeper. Civilization Revolution is a somewhat pared-down version of the awesome strategy game, but it's still got the empire building, trading, and various battles that you'll find in the main series. This lite version is great -- all it does is keep you from saving, so if you have the time to run up a full campaign, you can. The app was popular when it first released, so you may already have it, but if you haven't tried it yet, now's the time to give it a look.
It'd also be nice on the "Try Before You Buy" section to at least have links to the full apps -- you can usually find those by clicking on the "More iPhone apps by..." section of the App Store, but if Apple is specifically promoting demos, shouldn't they also promote the full apps. Anyway, the full version of Civ Rev is currently $6.99 on the App Store. That's much cheaper than the versions on any other system, so if you try the demo and really enjoy it, feel free to get the full app for the total experience. And if you like Civ Rev, do yourself a favor and head back to the main game -- Civ 4 is an excellent title as well, and the new version looks great, too.