I think it would be cool to elaborate a listing of all photo cameras able to output a full def./no overlays live video signal via HDMI. They could be an interesting alternative for fixed studio shooting.

It's not hard to guess that about all cameras (reflex or not) will probably have HD video recording and HDMI output in the next years...

Canon 5D MII: yes
Canon EOS 50D: ?
Canon S1 IX: ?
Nikon D700 : ? (i will try this soon with a friend)
Nikon D300 : ?
Nikon D90 : ?
Casio Elixim EX-F1 : ?
Panasonic G1 : (supposed to be full video HD enabled in the next version)?
Sony Alpha DSLR-A900 : ?