Dude, dude.
It's like, y'know?
Dude?

Ahem.

Anyway, I got a 4GB Kingston Class 4 miniSDHC for my N810.
They seem very happy with each other.
Monday I'll have a couple of these wicked cheap 4GB Class 6 Patriots from NewEgg, $25 delivered.
http://www.newegg.com/Product/Produc...82E16820220260
I will duly report back.

Bigger cards will come. Give it a few months.

There's also the option of the micro cards,
but some people have had trouble with the adapters.