If you haven't tried it, you should check out www.voicethread.com It doesn't create slides but it allows you to record voice annotations while you 'doodle' on the slides. There are some math examples there already. Make sure to check out the tutorial for the 'doodler'. The other cool thing is that you can invite other people, i.e. students to ask questions back. It's also an incredibly simple interface.
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If you haven't tried it, you should check out www.voicethread.com It doesn't create slides but it allows you to record voice annotations while you 'doodle' on the slides. There are some math examples there already. Make sure to check out the tutorial for the 'doodler'. The other cool thing is that you can invite other people, i.e. students to ask questions back. It's also an incredibly simple interface.