Google Mobile App for iPhone
Think of Google Mobile as Firefox 3's "Awesome Bar" for the iPhone. Not only does this search-bar-on-steroids suggest popular query matches for you once you type in a few letters, but it'll also search your phone for any contact names that start with the same few letters. Tapping a search result launches it in a browser window, and tapping a contact name lets you message or call them. For some reason, this app asks you to use your current location, presumably to match your search query with nearby businesses or listings, but in my testing it didn't really associate my searches to local points of interest.
Note: This link takes you to the vendor's site, where you can download the latest version of the software.