As you probably already know, SharePoint has great support for OData, providing access to lists, documents and all sorts of goodies.
I always seem to forget how the link to the OData endpoint is constructed, though. So I created this short bookmarklet that does the trick. Just navigate to a SharePoint site and click on it, and you'll navigate to the OData endpoint for it.
If you want to right-click to add to favorites, here is the link form.
You can then query directly from the browser or add a service reference in Visual Studio and write a full SharePoint-enabled application - at this point the sky's the limit.