Well I see Beekart released a some new homework! (Yay! :D)
And don't stone me for this, but I actually enjoy drawing skinnier bodies, mostly for the detailed shape, purely on an aesthetic level. Also, might I re-suggest posemaniacs as beekart did, it really gives you some awesome positions and you can rotate it however you want.
Pose maniacs was annoyingme. All the girls are in passive "sexy" positions... :/ agggggaaahhg
Hmm... I googled a bit, there doesn't seem to be a lot of alternatives. Maybe try something like this: http://reference.sketchdaily.net
It's timed, but I'm sure you can screenshot the images or draw fast. :P
Or i can keep drawing myself lol
This works!!! Still skinny girls but badass poses!!
Great, glad it works. :D