A short weekly announcement that says what is happening, what is due, and links straight to it keeps students oriented and cuts down on email. You can write these while you build the course and schedule them to display on the right date, so the communication runs without you remembering each week.

One detail to plan around: in Blackboard you can send an email copy of an announcement, but not for one scheduled to display in the future. If you want an emailed announcement, post it at the time you want it sent rather than scheduling it ahead.