Many people use Google not just for searching but also for news, weather, stock and even for keeping an eye on the latest movie in town. For this kind of use, iGoogle is perfect because it does all this - keeps tab on your Gmail account etc.
It works on most handsets with minimum fuss. It’s not a downloadable app, but rather a customisable Web page. And, while it may not look as jazzy as some of the others mentioned here, it’s hard to beat as far as its utility is concerned.