Android: We've featured one-click rooting apps for HTC phones, but free app Universal Androot will root a large number of Android phones with just a few taps, no PC or troublesome hacking necessary.
Whether you're stuck with a phone that requires the long, scary root method, or you have a one-click-from-your-PC method available, Universal Androot is the best new way to root your phone. All you need to do is download the app to your phone, install it using the package manager (make sure you have "Unknown Sources" checked in Settings > Applications), open it up and hit Go Root.
You'll need to select your Android version, and you can even do a Soft Root which only roots your phone for one session. After rooting, you'll be able to download root-only apps like Wireless Tether, previously mentioned SetCPU, and even install custom ROMs with ROM Manager.
Universal Androot is a free download for a large number of Android-based phones. Hit up the thread at XDA-Developers to see if your phone is supported, and grab an account at the forum to download and install it.
1-Click Root for N1 [XDA-Developers]