Google just released Chrome for iPhone and iPad and it's not a bad little browser. However, one problem is that if you open a link in another app your iPhone will always use Safari. If you'd prefer to use Chrome all the time, BrowserChooser is a tweak that lets you do it.
BrowserChooser lets you switch out the default browser between Chrome, Dolphin and more on a jailbroken iPhone. Setup is simple. Hop into the Setting menu, tap BrowserChooser, and tap the browser you want to use. Now, when you click on any link in any app (even if it's labelled "Open in Safari") it will open in Chrome or whatever browser you choose. You can find BrowserChooser free in developer Ryan Petrich's repository. In Cydia, tap Manage > Sources > Edit > Add, type rpetri.ch/repo and search for BrowserChooser.