hybrid Sli 9800 9600gt?

desktop cards. There is no such animal.
Hybrid crossfire - was a term to describe a combination of IGP and some discrete video cards. Basically all support for it is gone. It didn't return much performance and it had major stability problems.
Hybrid sli- would be nvidia products and they employed this like above in some notebooks. http://www.nvidia.com/object/hybrid_sli.html
You can't sli different Nvidia cards. In some cases 9800 1gb could be matched up with 512mb 9800. But not different models.

just like notty22 said you can only pair the same card in SLI regardless the memory config. i know what you mean but why want to combine 2 different card in multi gpu setup? even you can combine them (in CF) the faster card will be slowed down to match the weaker card.