Outlook, as much as it can bring a machine to a grinding halt, has a calendar (amongst a million other things), that can be shared across a team.
I’ve used that in the past to manage a team’s daily/weekly tasks. You can send out email reminders (which, admittedly, get annoying after a while), about meetings, scheduled deliverables, etc.
I had a look on SourceForge, CodeProject, and the usual sources, and nothing jumped out.
There is always MS Project, (which can, again, be way overkill), but it doesn’t really support an agile cycle (at least not the version I have).
B.