If you travel a lot, Triposo (free, universal) is a great addition to your app arsenal. Triposo has guides for pretty much everywhere, even out-of-the-way places for US travelers like Afghanistan, Chad, Latvia and Zambia to name just a few. In addition to country guides, there are city guides for most of the bigger cities around the world.
The app is basically a shell for region-specific data you download while planning your trip. Once it is downloaded, you don't need an online connection to use it.
The guide gives you an overview of the destination, along with detailed maps of its largest cities. The app includes a currency converter, weather and some useful phrases. In big cities, you get restaurant guides and suggestions for nighttime entertainment.