Talking to the Cortex M3 (Stellaris EKS-LM3S1968) under linux
The C compiler I use for my Cortex M3 is Soucery Codebench Lite Edition. There are some alternatives like YAGARTO. You need to write (or find) a linker script that fits your MCU.
You also want the CMSIS package for your MCU. That contains all the register definitions.
For flashing and debugging I use OpenOCD, this allows to use GDB as frontend for both tasks. The EKS-LM3S1968 board is shipped with a JTAG-to-USB chip supported by OpenOCD.