Project comparisons allow you to view any selection of projects side by side just like they're shown on regular categories or in search results. You can try out an example or start yourself by adding a library to the comparison via the input below. You can also easily share your current comparison with others by sending the URL of the current page.
GChart exposes the Google Chart API via a friendly Ruby interface. It can generate the URL for a given chart (for webpage use), or download the generated PNG (for offline use).