I've been helping jk with the
simple but wonderful bitfield (me helping
mostly equated to telling him what features I wanted, followed by him
telling me he'd already implemented them and then laughing at me).
We now have bash completion, vim modes and Debian/Ubuntu packages
which can be grabbed from here:
deb http://neuling.org/devel/bitfield/ ./
We are looking to improved the register database, so if you have any
register definitions you'd like added, email jk or even better, grab the Mecurial
tree and submit it as a patch.