O.K. I've got the following:
1) Nightly free opera webcast from the Met.
2) Virtual free expeditions daily from Linblad/National Geographic
3) DxO webinars
4) Daily webinars from National Habitat Adventures.
5) Daily webcasts (twice daily!) from Nikon Live.
And I know I've seen several more offered. Much of this stuff looks interesting and useful. Or just entertaining.
On Natural Habitat Adventures there was a guy giving an hour presentation on monarch butterflies based on his PhD research. Fascinating stuff.
The Met Opera webcasts started ten days ago and we haven't missed any of them. This is Wagner week and these operas run five hours!