FontBook, the veritable bible for typography addicts and design nerds everywhere, recently updated its iOS app to support the iPhone. You'll never be caught without an encyclopaedic knowledge of typography ever again.
What does it do?
FontBook is a near-comprehensive reference tool for exploring fonts and in any subclass you could hope for. With FontBook 3.0, we see, among other features, the addition of list views, an option to write your own sample text, and the ability to use search filters. Upon first opening the app, you're prompted to explore based on class, designer, year, foundry or usage, each one breaking down into a nicely laid out tree of subcategories. Additionally, you can search for specific fonts if you already know what you're looking for.