MSN to go
Since moving to the US I've become a real fan of MSN Mobile. Leaving aside that fact that data plans are affordable here, the information on the service is great - simply looking something up, or getting directions has become really easy.
My GPS isn't always the most reliable source of information so I've been using Live Search for Mobile to find the places it can't but now that the new Mobile MSN portal is available in beta I've been using the online services much more.
Mail, news, weather and local information. In the palm of your hand when you need it. What more can you ask for? Well, I'd like more web pages optimized for mobile browsing (hint Wikipedia... you have good information but often unreadable on a smartphone)
Once you've found a page then you can use deepfish to get a much better view on the content...