It’s not me, the guys of TehcRadar have ranked gvSIG mini:
An incredibly comprehensive mapping tool which combines many major online maps like Google, Bing, Open Street Map and more, which will win UK fans for one huge reason alone – it supports the official and recently open-sourced Ordnance Survey data. This means you’re never more than a post code search away from seeing where you are in OS-level detail, which offers much more in the way of accurate local data than other map tools provide.
A lot of kudos for my colleagues of Prodevelop who are doing an amazing job bringing to the android and J2ME community a great application but also a free software available to anyone under the GPL license.
If you don’t know what gvSIG mini is, take a look on this video and see what it can do for you on a regular Android phone: