In case you are wondering, there are still lots of other vendors that offer a choosy range of machines preinstalled with Linux for your convenience. The following 5 are just a sample of the lot
This site has a respectable array of desktop and laptop computers fitted with Ubuntu Linux ready for use. Prices start from $399 and you can also customize each machine to fit your hardware specification tastes at an extra price. They also other Linux peripherals like audio players (another name for iPod), cameras, printers among others.
This site also has a range of laptops that ship with either of six distros namely Ubuntu, RedHat, Centos, OpenSuse, Fedora and Oracle Linux.
All the machines are also customizable to your taste for extra bucks. They also offer an optional dual-boot configuration with Windows for those who need the latter for special reasons.
One of the most popular Ubuntu centric OEMs out there, ZaReason stocks a wide array of machines; desktops, laptops and servers to suit various needs and specifications.They also stock some peripherals to add some spice to your machine.
According to this company
"EmperorLinux provides Linux laptops with full hardware support under Linux. Since 1999, we have supplied systems to a wide range of customers, including engineers, physicists, mathematicians, and astronomers at over 50 different government labs and over 200 universities. We have supplied hundreds of corporate clients, as well. If you use Linux in these environments, EmperorLinux is your sole source."System76
Another of the well known Ubuntu centric manufacturers, System76 has some of the widest assortment of Linux machines out there. Their flagship machine, the Serval Professional is a machine that will make any geek go green with envy.
There are a lot more niche manufacturers that gladly ship computers preloaded with Linux. They may not have the clout of Dell, but they do a good job of giving you value for money and from what I have read, unparalleled support in your use of their machines. If you ever think of buying a Linux machine, you might want to give any of these a try!