You can get the kernels with the "getkernels.sh" script. It works with the /dev/mmcblk0 device, or with an image of the first 32MB of the device (you can use dd if=/dev/mmcblk0 of=/mnt/us/dev/mmcblk0.img bs=4K count=8" to get that image (which also contains uboot images so it good to have).
Also, I like to modify my dd commands a bit to make them run faster (mmc writes are slower than reads). Here is a typical command I use (as I recall):
dd if=/dev/mmcblk0p1 bs=4K|tar czvf mmcblk0p1.tar.gz -
This is why my images tend to be in tar.gz files, BTW.
