Rooting Android: HTC G2
Android phones are popular nowadays despite the patent infringement issues surrounding them. One reason that they are so popular is their hackability. Most Android devices can be rooted so that the user has full control over the hardware. Custom software can then be installed on the rooted phones. For instance, a rooted phone can be backed up using Titanium Backup. A customized version of the operating system can remove the bloated carrier-installed software on the device.
I have the HTC G2. It came with an operating system that was pretty much stock Android, with very few customizations. I didn't like how plain vanilla it was, so I installed the HTC Sense 2.0 software that was installed on the European version of the HTC G2. I also overclocked the processor from the default 800 MHz to 1.4 GHz. Overclocking a smart phone sounds stupid, but the snappiness of the user interface and the quickness of the web browsing would change your mind.
Rooting is not for everyone. If you do it incorrectly, you risk destroying your phone. If you decide to root your phone, do your homework first. Go on over the XDA Developers to read up on your device before you attempt to root the phone.