After lots of looking around, I finally found a CAML query generation tool that supports SharePoint Online authentication and Client Side Object Model api. It also works with SharePoint 2010. It is well designed, easy to use, and very powerful. At the click of a button it gives you the applicable Server Object Model code or Client Side Object Model code or even Web Service code. Unfortunately, the generated code does not work with SharePoint Online, but that is because it uses different authentication.However take a look at my post on using authenticating against SharePoint Online when using the Client Side Object Model.
Thank you to Karine Bosch for writing the CAML Designer and making it freely available AND giving good documentation on it.
Click here to learn more and download.