Preview Site on Mobile

Are there any tools to preview what you’re site looks like on a Android or iPhone ? I know there are a few variations of screen size mobile phones. Has it become more standardized whereas you design for the biggest Android / iPhone and the page will resize to the smaller screen Android / iPhone ? I know more and more people use there Android / iPhone and basically use it a replacement for a computer.

I use a few tools here.

but then again I have a Droid and my friend has an iPhone so that helps too.

thanx !