Folks, 

Most all large conferences offer recording of the speakers. There are never
visuals or copies of the slide show offered. 
There should be a release written in the contract signed when the speaker is
hired. This is in the contract I receive whenever I perform at a music
festival, because those events are recorded for their archives.
I've been to nursing conferences, health conferences, and farming
conferences where this is done. The recording company makes enough to cover
the costs of equipment and time. In some instances the recording company
loses money.
The audio quality is not always great, but this depends on the venue and the
way the speaker uses the mic. Audio tapes/cds can be a great tool, but do
lack the understanding of seeing the slides and the speaker in action.
Now if you wish a copy of the slide show or the notes, you will have to
correspond directly with the presenter.

Hope this all helps.
Alf Bashore

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