The evasi0n jailbreak tool is available for Windows, Mac and Linux, and should work for pretty much any relevant iPhone, iPad or iPod, including iPhone 3GS, 4, 4S, 5 / iPad 1G, 2G, 3G, 4G / iPad Mini / iPod Touch 3G, 4G, 5G, where "3G, 4G, 5G," etc. stands for the generation of the device and not its cellular technology.
Naturally, before you proceed with the jailbreak process itself, the evad3rs team kindly asks you to make a back-up of your device in the unlikely event that something goes wrong. Other than that, jailbreaking using evasi0n is pretty simple. You just have to connect your iPhone, iPad or iPod to your computer with the USB cable, then use the option "Erase All Content and Settings" (that's said to make the jailbreaking process faster), and then finally start the evasi0n tool on your computer and hit the "Jailbreak" button. As always, please note that you are using this tool at your own risk - PhoneArena or the devs of the tool are not responsible for any bricked devices. Though we are going to feel sad, should we hear that you've accidentally bricked your handset or tablet. :(
Also, please do not jailbreak your iDevices just to install pirated apps. This way you'll be damaging the entire iOS ecosystem!
Download: evasi0n for Windows | Mac | Linux