This guide is out of date; the new version can be found at https://thegbill.wordpress.com/2010/07/26/spirit-linux-revised/
P0sixninja has successfully ported the Spirit Jailbreak (previously only available to Windows and Mac OS X users) to the ever-growing Linux operating system platform. The port, which can jailbreak all iPod Touch, iPhone, and iPad generations at 3.1.3 firmware, is also the first untethered jailbreak for most models. I will quickly explain how to download, build, and use the Spirit jailbreaking utility on your Ubuntu 10.04 desktop.
- Press Alt+F2
- Type in gnome-terminal and hit enter
- Install git and other build tools by issuing the command sudo apt-get install build-essential automake cmake git-core libusb-1.0-0 libusb-1.0-0-dev libgtk2.0-dev libgnutls-dev libcurl3-openssl-dev ifuse libxml2-dev python-dev – enter your password when prompted
- Download this package of dependencies to your desktop
- Now unzip it by right clicking it and pressing Extract Here
- Now just enter the commands as I tell you to
- cd Desktop/Depends
- cd usbmuxd
- mkdir build
- cd build
- cmake ../
- make
- sudo make install
- cd ../
- cd ../libplist
- mkdir build
- cd build
- cmake ../
- make
- sudo make install
- cd ../
- cd ../libimobiledevice
- ./configure
- make
- sudo make install
- ignore the ifuse package — it is not needed as it is provided in the official Ubuntu repositories
- cd ../
- Next, type in git clone git://github.com/posixninja/spirit-linux.git
- Now, enter in cd ./spirit-linux
- Run make
- Plug in your iDevice
- Run ./spirit to jailbreak your iPod Touch, iPhone, or iPad
- Now just let your iDevice restart and wait while Cydia is installed on your newly jailbroken device!
The GBill 
