I’m pretty happy with Google maps, but if you’re seeking a good alternative, Nokia’s just made a web app of its mapping service available in-browser for both iOS and Android. It’ll even do some things others can’t, like let you to save parts of a map for offline usage and give you voice-guided walking navigation.
As a web app it’s pretty decent, and behaves similarly to native apps (at least on iOS), just in your browser. The walking voice-navigation is geared up for guiding you around the mean streets of a sprawling urban landscape, so it’s not going to do too well if you’re in a car. It will spit out driving routes though, and gives you a live traffic view and “public transport view”, which shows you things like Tube routes in London.