If you are looking for an android firmware flashing tool like ODIN for Linux or MAC, free cross-platform utility Heimdall is the answer. While Odin is a leaked internal Samsung software, Heimdall is an open-source, cross-platform tool suite to flash ROM's onto Samsung Galaxy S devices - Heimdall uses the same protocol as Odin but is easier to use and supports cross-platform operation.

Here is an step-by-step illustrated tutorial on how to flash the latest Heimdall stock firmware packages for GT-I9000 (2.3.5, XXJVT) on Samsung Galaxy S I9000.