Sure there are plenty of iPhone web-apps you can visit through Safari, or even bookmark so you can visit them later, however navigating through bookmarks doesn’t really fit the UI flow of the iPhone.
Let me introduce you to appleopolis.
appleopolis is an iPhone launcher that lets you add “widgets” to your dashboard. It’s UI is similar to the Home screen and thus visually appealing. The real kicker is that it launches your favorite bookmarks while keeping it real with the iPhone’s user interface. I’ve got Digg and Meebo for sure on my dashboard – what do you have?