So at least for this month, my new favourite system of all time is now Apocalypse World. It's well worth checking out. It strikes me as a very freeform style of game. The playbooks (combination character sheet and sort-of character class) remind me of a freeform character pack, but with a decent amount of customisability.
I've made a start on some playbooks for a game set in Glorantha. Comments and suggestions welcome.
http://goo.gl/ZFUbX
Simon Hibbs