They say that when in Rome you should always do as the Romans do. Well, I'm not sure PDAs were around in Roman times but if they were them I'm sure Caesar, Nero et al would have the Rome DK Eyewitness Top 10 Travel Guide & Map installed on their mobile device.
Based on the popular Dorling Kindersley Top Ten travel series, this guide to the Italian capital is presented in an interesting and enlightening manner. Split into different sections, such as Highlights, Around Town, Streetsmart and Top Ten, the guide dishes up lots of facts and advice in a different style to the those stuffy old guidebooks.
The Top Ten section is my personal favorite because it helps you prioritize places of interest, meaning that if you're on a tight schedule you can make sure you see only the best squares, churches, museums, etc.
Getting around Rome is made much easier thanks to the inclusion of zoomable road maps, bus routes and Metro stations. There's even a map of the area surrounding the city in case you want to explore a bit further afield.
Although the main interface is a little bland, the inclusion of a searchable index means that it's pretty easy to find your way around this guide.
And likewise, this DK Eyewitness Top 10 Travel guide makes it pretty easy to find your way around the best sights of Rome.