But what to post? Here's the things I post about between games.
Monologues - There's often I time after or before an adventure when an NPC is going to speak at length. Perhaps it's a long adventure introduction or maybe your party has just finished off the main villain and he's spilling his guts. Either way, posting the monologue gives all your players the opportunity to read it at their convenience. It's also a good way to handle extended Q&A with the bonus of having a record of it for future reference.
Location information - Often players will end or begin an adventure in a new town. I like to post all the details of what is in the town as well as what can and cannot be purchased. Then players have the opportunity to do stuff in the town that is not combat related. This can save a lot of time at the beginning of sessions.
In between game events - sometimes I try to run it in between events. Sort of mini adventures that are designed specifically for play by post.
Experience and other rewards - Often it's too late to calculate experince or divide up treasure. I'll post the info the next day and players can discuss how to divvy up the spoils.
Between game trade: - Handling all the selling and buying in between game saves a lot of wasted time on game night.
Bonus: Player Character Pages
If your players are willing, have them create pages for their character, and create your circle with those pages instead the player's main account. Then they can customize their icon and other info, plus all your in game post are neatly organized on off your main stream.
Bonus: Use Hangouts
It's hard to get together for the in person games. People are busy. Some groups only get to play once a month (or less). Supplement your games with shorter sessions using hangouts. It's not as good as getting together at a table, but it's the second best thing. Try using a few of the online game tables that use goolge+ hangouts suchs Table Forge or Roll d20.
A Google Doc of this blog can be found HERE. Feel free to comment on it.