I'm sure you hear this a lot - but this is a great feature for Calibre. Thanks!
I have seen some collection programs for the Kindle, even tried a couple, but they seem to lack something. I downloaded non-GUI version and it worked fine. Then I notice a GUI update a couple days later. This version is fantastic. I have been playing with my collections and getting no reading done. I must have changed my collections 10 times so far. It is just fun to use.