Many of the ideas discussed here, while sound, have one fatal flaw: they reward the do-nothing character just as often and as well as the character that sticks its neck out. So where's the in-game benefit of taking a risk?
Keeping the party all the same level regardless of any other factors just isn't that important...if a few characters have, in the long run, done more and-or survived longer, they *should* be higher level than their less-involved and-or newer replacements. And there's a fairness factor to consider: if Joe's played in your game since Day 1 and has run his character from raw 1st all the way to 12th, why should I as a new player expect to be able to bring my PC in also at 12th, without having done all the work to get there? (now, if once I come in, my PC does enough to eventually catch and pass Joe, that's different...)
That said, there's some good ideas here about what ExP should be given out *for*, other than straight combat...I might swipe one or two...
Lanefan