Im using heimdall in Ubuntu 10.10. I made this video as an example for anyone having trouble and I've seen a few people asking about heimdall. Also made this cause I soft bricked my phone and flashed the unmodded JK6 3e kernel.
Its really easy to use. Any questions or comments, feel free to leave them. Ill try to answer best I can. I'm known as FlyingPoo on the TeamWhisky forums/IRC.
Edit: you can flash just the zImage without putting it in a .tar file. As Benjamin Dobell and some associates over at TeamWhiskey say you CAN flash the files directly. With that said If you download a kernel that is "odin flashable" you can flash it still in the .tar file.