Latest FIASCO is PR1.3 RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM

Latest EMMC is RX-51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM

Flasher tools here


Once you have the flashed the above two following instructions here, CSSU is pretty recommended. You may want to choose CSSU-Testing if you are willing to experiment a bit and then choose CSSU-Thumb which speeds up the N900 tremendously.