You spend a lot of time perfecting the lectures you give in face-to-face classes... that should mean you need something similar in the online classroom. Why do you include lectures in your teaching repertoire though? What is the purpose exactly?
- Clarify the sticky parts of the course.
- Add material that is not included in the text.
- Emphasize the material that is most important.
- Keep momentum going in the course.
- Add applications and current events.
I am sure there are other reasons for lecture as well, plus you use class time to go over exams and homework, have students do group work, etc.
There are several places to put lectures in an online course. First, you could develop a set of taped or written lectures (say Powerpoint with voice-over) and put them in an specific content place. Clearly this is a good way to handle anything that can be developed once and used for several semesters. It is a good way to add any material missing from the textbook and to clarify sticky spots in the course. On the other hand it doesn't do anything for momentum and current events.
You can develop a weekly (or twice or thrice weekly) announcement - again either written or recorded - that discusses current material. In Blackboard this can work particularly well because you can automatically email each announcement to students. This reminds them they are in a class and that they need to stay abreast of requirements. The drawbacks are that email doesn't handle video well and that the announcements are also a good place to handle the housekeeping details -- due date reminders and such.
Last is the discussion option. You can break your lectures up into sections and use them as discussion starters. To do this start a discussion thread with the first part of a lecture, ending with a question or two that you commonly ask students. Discuss that for a day or two, then post the next lecture section, again ending with a question or two. This can be very labor intensive, but is fairly effective.
The other option is to break the lecture into sections and post each as an individual discussion thread. For some reason though the multiple discussion threads seem to be off-putting or frightening to students. It also eliminates some of the conversational aspects of the single thread as too many student respond in the same way to each question instead of moving on.
Personally I use all of the above, depending on the type of material. What's your favorite place for lectures?