How can I get an Arduino board?
See the howto for options, which include buying a board or building your own from the information on the hardware page.
How can I run the Arduino IDE under Linux?
See instructions for Ubuntu Linux, for Debian Linux, for Gentoo Linux, for Linux, or for Linux on PPC. This this forum thread has more information. Or, you can use Arduino from the command line, and not have to install Java.
These questions have moved to the troubleshooting section of the Arduino guide.
How do I burn the bootloader onto my board?
See the bootloader page for details on burning the bootloader onto an Arduino board.