Earthdawn explicitly includes a system where players who keep a scribe or cartographer among their characters to chronicle their journeys get a reward.
My one caution to doing something like this is to make sure that there is something that everyone can do, or distribute the rewards evenly (or at least sanely cap them) so that there's no huge boost to one player at the exclusion of others.
In my experience, everyone can bring something to a group, regardless of their abilities. You can have one guy handle the bookkeeping (I like to keep a running tally of everything players have gotten through the game so that if people die they can make a character who's back on level, should the setting make sense that way) for the players' party; checking his notes against some cursory ones you have can help tell you if a player "accidentally" (or sometimes legitimately) forgot that they'd already applied certain changes to their characters. It also helps catch up players who had to miss a session (not always necessary, but again, it depends on the game).
Cartographers and scribes are also important. I like to give these roles to the more analytical players in my groups; they're the ones who are obsessing about where everything is in combat, and letting them draw maps and track whatever they care to write down (I have some players who will do this in meticulous detail, like a log on a video game) will give them something to do other than metagaming, which tends to be a problem with them otherwise, plus it gives me a lot of reference for if everything's working correctly.
Then, finally, there are artists and chroniclers, as I call them. They're the fine arts people of the group who essentially help to create a log of what's going on. They make all the drawings and such for characters and important things within the campaign (usually with my feedback, though I had one player who basically made the rough sketches of an anime based off a Shadowrun campaign without requiring any feedback, though it was interesting to see how they got different things from the story than I intended them to). Chroniclers may not be comfortable in another role (they may not know the system well, or be rookie roleplayers), but they're more than happy to keep a less mechanically informed history of events, and they're crucial to GM's for making sense of what your players know and what they don't-for instance, if you accidentally let some important information slip out without meaning to.
Finding in-character things for these people to do is important as well; the fighter or cleric may be the guy in charge of recording injuries and maps, since he's up ahead taking and dealing out damage, while the wizard is responsible for handling the finances and making sure that people are keeping up on their training outside combat. The bard, obviously, will be the one to recount stories, but other characters may enjoy doing it as well (barbarians who share tales around the campfire, stuff like that). In my experience, the more you can handle in-character, the better, especially since it helps give extra depth to the characters.