The Linux operating system comes in a variety of distributions, from novice and user-friendly to advanced. Most distributions can be installed onto a variety of mediums such as CD, DVD, USB, external hard drive and SD card. If you have an Asus EeePC with an SD card slot, you can download and boot Linux from it using a free application designed specifically for this task.
Download UNetbootin (seeResources). This is a unique application with access to at least 40 different Linux distributions and the ability to install any of them onto a variety of media.
Insert your SD card and launch UNetbootin. Click the drop-down menu next to "Distribution" and select the version of Linux you want. Next to "Type," select your SD card. Press "OK" to download the chosen distribution and install it to your SD card.
Restart your EeePC and press "Esc" to enter a boot menu. Select "SD Card" from the menu and press "Enter." This boots your computer into Linux from your SD slot.