There are many, many Linux ports:

• Intel 386+ (of course) with support for ISA, EISA, PCI, VLB, and MCA (and Merced)

• Alpha (Linux is 64-bit now)

• Motorola 68030+

• Power PC

• ARM

• SPARC

• MIPS

• SGI (in progress)

• VAX (in progress)

• PalmPilot (in progress)

• 8086-80286 (in progress)

• And more!