JiWire Wi-Fi Finder: JiWire locates wireless hotspots around the world.
Glide Mobile: Glide is an online office and collaboration suite that allows users to create, edit, and share all kinds of documents including word processing documents, websites, photos, contact lists, calendars and more. Google Docs and iZoho offer similar capabilities (although read-only).
Gas.app: Gas.app lets you find the gas stations with the lowest price anywhere in the US. A great companion to Gas.app is iPhone Miles, which is an easy-to-use mileage tracker.
Movies.app: Movies.app lets you browse all movies showing in all theaters in your area on a specific date.
Movies.app integrates with Maps for location information and also links to trailers and IMDb information for each movie. It even lets you buy tickets online via MovieTickets.com.
Google Mobile: Google’s Web-based tools including Gmail, Google Docs, Google Calendar, Google Reader, Google Notebook, Picassa, and more.
iPhlickr: iPhlickr - a simple and streamlined iPhone interface to photo-sharing site Flickr.
Mundu: Mundu allows users to chat using AOL Instant Messenger, Yahoo Messenger, MSN Messenger, and Google’s GTalk. (also try Meebo)
Listingly: Listingly is an online list manager.
uPhoneHome: uPhoneHome is an application launcher for the iPhone. (also consider mockdock)
Social Networking: Facebook, Multiply, and Twitter (via Pocket Tweets or Thin Cloud) are all traditional social networking sites that have dedicated iPhone application access. There are also new social networking sites designed specifically for iPhone users, including iRovr, iPling, and iPhone Colony.
Visit Apple’s web apps directory to find more iPhone applications.