There are many websites out there that offer iPhone-optimized views. But I bet you haven't seen anything like Steve Streza's latest creation, Swearch.
Swearch is a neat little web app that lets you search on a variety of search engines: Google, Twitter, Wikipedia and Flickr. As you search through them, the app will display results in full screen - cool. But that's not the big deal about Swearch: you can switch back and forth between these services with a simple swipe on your iPhone, and the developer also made sure to include some beautiful, Retina Display-ready, custom backgrounds for each service. Check those clouds in the Twitter page - neat.
Swearch might not be the app you spend all the day playing with, but it's well worth a webclip icon on the homescreen. Anytime you need to search for anything on the supported services (Streza promises that even more are coming in the future, together with iPad support) you can just fire it up and start typing.
Again, open Swearch.me from your iPhone and enjoy. I'm pretty sure this is one of the most clever web apps I've ever installed on my iPhone.