Busybox should have a --create-symlinks-in=/sbin feature, but for now…

    ./busybox --help | grep 'Currently defined functions:' -A30 | grep '^\s.*,' | tr , '\n' | xargs -n1 -i{} ln -s busybox {}

update on 2012/03/22: Shawn Hicks points out that this works better (unverified by me):

    ./busybox --help | busybox grep 'Currently defined functions:' -A30 | busybox grep -v 'Currently defined functions:'|busybox tr , '\n'|busybox tr -d '\n\t'|busybox tr ' ' '\n'|busybox xargs -n 1 ln -s busybox

update on 2012/10/07: Nicholas Fearnley further updates the recipe to this:

    ./busybox --help | busybox grep 'Currently defined functions:' -A300 | busybox grep -v 'Currently defined functions:' | busybox tr , '\n' | busybox xargs -n1 busybox ln -s busybox