Google has the strange habit of removing features and killing services only to resurrect them after a few months. A lot of people complained when Google Calendar removed the gallery of public calendars. Google's explanation was that few people used that feature and it was difficult to internationalize it.
Google Calendar's gallery isn't back yet, but you can now subscribe to sport calendars for baseball, football, soccer, rugby, hockey and basketball. How to find the new calendar directory? Click on "add" below the list of "other calendars" and select "interesting calendars".
Like Gmail, Google Calendar is now a container for iGoogle gadgets. To enable gadgets, go to Google Calendar's settings page, select "Labs", click on "Enable" next to "Add any gadget by URL" and don't forget to click on "Save". You'll see a small box that lets you enter the URL of a gadget. It's not user-friendly and Google forgot to list some samples, but you can try this Wikipedia gadget:
or this gadget for driving directions: