Jailbreaking Update

To jailbreak the 2.1 firmware on Windows, download QuickPwn. If you want to unlock your iPhone, you will need to download bootloaders 3.9 and 4.6. You can download those at iphone-hacks.com. There is a new version of iPwn for Mac that can jailbreak and unlock firmware version 2.2.

Jailbreaking

Most people know what jailbreaking an iPhone/iPod touch is, but only about half of the owners have jailbroken their devices. Why not more? Because they don't know the facts. Fact: no iPhone or iPod has been broken trying to jailbreak it. Fact: many people are scared of losing their warranty, so they don't jailbreak. Fact: there are many different programs that let you un-jailbreak your device if you need your warranty. If you ever need your warranty, re-virginize your scripts(download an app for this off Installer or Cydia), then restore your device.
To jailbreak your device on your computer, download iPwn for Mac, or WinPwn for Windows. There is a short intro form on how to use these once you download them.(Don't worry, they are not buggy and will not mess up your computer. No comp crashes EVER reported.) Once you have jailbroken your device you can download non-Apple indorsed apps via Cydia or Installer v 4.0(these were where Apple got the idea to create the AppStore from). And you can still use the AppStore.