The quickest and easiest way to jailbreak your iPhone is by going to the following website. Now this may or may not work depending upon the version of firmware that you have. Use the slider to start the download process and install.
Go to jailbreakme.com on your mobile divice first: go to google and search open app mkt then add it to your home screen after that open it up and search cydia installer find the one from tower group and add it to your home screen open it up and in cydia search jailbreakme
Actually you cannot jailbreak without computer. If you have iPod Touch follow this website. http://jailbreak-ipod-touch.net - Do not use jailbreakme.com or blackra1n for jailbreak your device. Because these old tools are now not functioning. If you use those tools device may be brick.