I will reward players for anything that they do outside the regular game session that substantively adds to the game. This includes painting miniatures, collecting pertinant setting information, creating a spreadsheet showing the various Jump check results and for writing character journals.
Toward the end of my last campaign, I had the idea of letting the players write up "After Action Reports". Basically one or more of the players jotted down notes of what happened during the combats that took place in the game. After the session, they gave me the notes and I used them to write up the Story Hour posts. Since I was often writing the Story Hour weeks after the session took place, these reports were a huge help in me remembering what exactly took place during the combat.
I will definately be keeping that idea when we pick that campaign up next month.
The XP I reward for these things is part of the alternate system that we use to reward combat, goal achievement, social interaction, skill use, etc. It just represents one other category that we call "creation" (i.e. creating something substantive to contribute). As such, I'd say that characters who do it get anywhere between 75-150 XP each session for it.