Q:

What kinds of player contributions work well and under what circumstances?

Introduction
In Amber diceless roleplaying game players get extra points for building their characters by committing to player contributions, such as: Writing a diary, writing game reports, drawing character pictures as Trump cards.
In Amber diceless, players get points at character generation, which is problematic if they later find out they over-committed and can't keep up with their tasks, or are simply lazy.
Other examples might include writing a newsletter, bringing snacks, allowing people to play at your house.
Question
Let me call out-of-game tasks that players do for in-game rewards with the name of player contributions.
What kind of player contributions have worked well, in what sort of games? Correspondingly, when do player contributions fail badly or fall flat?
By working well, I mean that it encourages players to do the task and not feel like they are doing unpleasant homework.
Motivation
I am designing an old school adaptation/severe mutilation of Solar system (newer edition of the Shadow of Yesterday), where players get experience for triggering keys. I am going to only give experience once per session per key and intend to tie some of the keys to both out-of-game player contributions and fictional events.
For example: 1 xp when you draw dungeon maps during the session, 3 xp when your character makes them publicly available in the fiction and you, the player, make the maps publicly available to all the players.

Please note that the question is subjective (but hopefully not argumentative). As responses, please give personal experiences or cite some other credible source. In particular, I am not interested in "My favourite game also has player contributions! Check it out.", but I am interested in "Here's an actual play report that touches on the issue of player contributions. I found it helpful because of  these reasons."

A:

I am playing in a GURPS campaign right now, and we are managing our campaign using the wiki and other features on obsidian portal. We have a few player contribution opportunities right now. Since GURPS is a point based system, points are rewarded for these contributions. Note that we were encouraged to write lore for this world and the DM would integrate the lore in to the campaign.
At the start of the campaign, we were awarded points for having our characters up on the wiki and properly formatted. Another bonus point if you added at least one significant page to the wiki for world-building (I did Theology and wrote about the world religions).
The DM encourages us to write a journal for each session. The player with the best journal entry for each session (as voted on by the players) is awarded one point. If nobody does a journal entry for a session, EVERYBODY loses one point.
Thus far these have worked out well, although not everybody participates in the journal every week.

A:

Some tasks that really help:

Blue Booking/Game Recapping: In my group, it is not unheard of for us to play into the wee hours, and someone gets sleepy (typically me, but when it's not, I try to bluebook for those that don't "roll well on their save vs. Sleep")  I typically send an email summing up the evening's events in something less than a page.  Typically we get bogged down on roleplaying, so an hour of roleplaying can be summed up to "the group had a lively discussion on whether we should avoid, or invade the kingdom across the river".  It keeps everyone on the same page, but if you nap, you miss out on most of the in depth stuff.  
snacks: We have a few dietary issues in our group, so either diabetic friendly snacks (home made or store bought), or home made snacks of the NOT diabetic friendly are generally welcomed.  Store-bought snacks tend to be looked at as ho-hum, unless it's a birthday cake from the fancy grocery store in town (cough, Whole Paycheck, cough).
alcohol: Whether homebrewed (guilty!) or storebought, widely seen as a bonus to our group.  But we are all in our 30s, are married, and most of us have kids
Hosting: In my current group, the hosts have 3 kids (10, 6, and 1).  In the past I've hosted (bachelor).  Either way, you have to clean up before everyone shows up, then clean up again after everyone leaves.  It's a significant effort.
mapping: If someone maps in our group, the assumption is that it will be shared.  With 1 exception, we never have had "personal" maps.  Even the 1 exception, pretty soon after we realized that we could trust each other, we pooled maps and came up with a master map.  But since you mention more XP for sharing the map, so I guess maybe we are an anomaly.  Most often, however, we don't map things out to the nth degree, we'll just use the GM's battlemat and minis.  If we need to refer back to it later, the DM typically just gives out a copy of the master map.
extra books/dice/pencils/pens/erasers: It's more or less expected to bring your own, but we frequently have extras in case you are either not at "your" seat, or forgot. 
dinner: whether pizza, grilling, or cooking something from scratch, it keeps the group on task (at least our group of 5 tends to take an hour to decide where to order dinner from and then put together an order from that restaurant for take out).
NPC playing: Your character is killed and the villain is taking too much attention from the DM to play fully?  You just became the villain.
Co-DMing: In some cases we have even toyed with dual-DMs in games where everyone goes their own separate way and it tends to take most of every other week to bring everyone back together again.  If someone volunteers to not play a character, but to 2nd chair DM, they will know the adventure enough to know the broad strokes, and can take lots of the DM load off of the DMs shoulders (in game).  A married couple in our game did this to great effect, I assume they discussed the plot both before game and then after game so both stayed on the same page, but it was quite effective.

A:

A small but very useful player contribution not so far mentioned is character backgrounds. Good, involved character backgrounds can do wonders for helping a GM engage his players. Typically, I reward good backgrounds with some type of small item reward that is great for a first level characters, but not a big advantage at higher levels. This reward is tuned toward fitting their back story.
Examples include:

A fighter's sword that got handed down for five generations is actually masterwork
A extra skill rank in a non-essential skill like Craft: Adult Beverage
A couple of hundred gold in alchemical reagents
A points of fire resist for past dealings on the plain of fire
A better than average horse for player who grew up on a horse farm

