MicrostockCharts.com  is a free service that allows microstock contributors to record their monthly sales, downloads, sell through rate  and the size of their portfolio. Users can then plot graphs of these statistics along with other values calculated from them (RPI , Return per download, total earnings and total downloads).
Plotting graphs of these values is common amongst microstock contributors. It allows you to more easily see things like how well your portfolio is growing, the effects of a change of image style you might have recently adopted, how much you can invest on taking a photo to break-even on average. etc.
A quick look at my blogs and links page  reveals links to several photographers who at the time of writing this dutifully sit down each month and update spreadsheets and plot graphs before posting them on their blogs.
MicrostockCharts aims to make the process of charting, comparing and optionally sharing your data easier by becoming the standard place that photographers store their sales figures. The initial version of the service provides little more than can be done with a spreadsheet (provided of course you want to spend the time creating one). But future plans for the service are quite exciting.
At present you can optionally share your sales charts (everything is private by default) with anyone online via a simple url you can set on the site (example ). You can also choose to publish your charts with or without figures allowing others to view your trend data and compare earnings across agencies without disclosing your actual income to the public. Future plans will allow you to compare your data to aggregate sales from other users hence allowing you to see if the changes in your figures are reflected across all users e.g. you had a good month, or an agency has started a new ad campaign so sales are up across the board.
The site also introduces (currently in development) the concept of trusted microstock contributors, so you will be able to compare your sales against those of all users (anonymously) and those from users who have been marked as 'trusted' (i.e. more reliable data) by microstockcharts.
I'll be updating this post as new features are added. I also plan to start adding my sales figures to microstockcharts, I'll place a link to those here also.
Feature requests and planned new features  for microstockcharts.com (uservoice)
Introducing Microstockcharts  at MicrostockDiaries
Microstock Charts Discussion  board at MicrostockGroup