I might be willing to offer pony pictures as a motivator for projects I deem valuable, if that was intended as a serious possible reward and not a silly one.
It is both silly and serious. Silly in that I find ponies silly and serious in that people would be motivated by it (I definitely want one at some point).
Judging by the number of upvotes, Brandon Reinhart's analysis of SIAI's financial filings is valuable to quite a few people. Similar analysis' of Alcor and the Cryonics Institute would be quite valuable. There has been talk of more work on condensing LW content and placing it on the wiki. I'm sure lots of people would like to know about the literature on low dose asprin. People seem to want a front page more accessible to newcomers. Will these projects get accomplished? Some of them, but probably fewer than optimal. I think we can do better.
I would like to look for ways to channel group willingness to contribute to a project into focused individual willingness to work on a project.
Observations about the problem space
The following is based on discussions at the Seattle Less Wrong meetup.
Many people would get a moderate amount of benefit from such projects, but only a small number would end up putting in the hard work to make them happen.
The people most enthusiastic about a given project may not be the best people to work on the project. Perhaps they have very time consuming jobs or have a hard time being objective about the topic (e.g. someone who gets especially emotional about Cryonics) or have too many other projects already or perhaps they are intellectually motivated but not emotionally motivated by the project which might make it difficult to Get Things Done.
Trying to generalize too early is a risk here. Going out and building fancy tools or otherwise trying something elaborate is probably not a good idea at first. Better to try some concrete trials first and learn from those experiences.
Sources of motivation
There are three major potential sources of motivation: Money (the unit of caring), social status (Karma, kind words etc.), things (pizza, books, cookies, pony pictures).
Different motivators may work better for different kinds of projects. For example, money might be a counterproductive motivator for social projects but a great motivator for setting up a website.
How have others tackled this?
This is a problem others face as well. How do other similar groups and communities ameliorate it?
Miscellaneous observations
In the interest of Holding Off On Proposing Solutions, please take a moment to try to identify features of the problem space that I have not mentioned before reading the comments. Please mention any features you notice as well as any potential solutions or parts of solutions in the comments. I have some ideas, and I will propose them in the comments.