Conditioning is one, Open Gym or OTA would be one, Camp would be one. I use the calendar to schedule all of my team's events whether they are in-season or not so there is a need for more than games or practices. Even a Misc. category with a field that could be filled in would be helpful. That would enable team meals or non-athletic activities (like a fundraising day or community service day) to be scheduled.
This implementation should allow the events to be visible and announced year-round, Currently announcements only go out if the team is in it's current season/term.
We recently added the ability to create general events in the athletic calendars. You can add an event Title as well.