canonical download locations for MLO and u-boot.bin?

since part of my presentation will involve showing attendees how to
set up their own SD card, is it fair to say that this is a fundamental
location for some of the essential binary images?

and that (as i asked in an earlier post) the SD-version form of those
files is distro-independent?

  also, i'm aware that there are NAND versions of those files and
that, if one got clever, one could set up an SD card without MLO or
u-boot.bin since you can use the ones in flash, but i'd rather keep it
simple so i'm going to suggest that, unless there's a compelling
reason, if you're working off of the SD card, there's no need to mess
with the MLO or u-boot currently in flash and use everything off of
the SD card. is that a fair generalization?