For the record, I got this to work on my n810:

Sandisk MicroSD to MiniSD Adapter
http://www.amazon.com/gp/product/B000TLXCDW
SanDisk 8GB microSDHC Card CLASS 2 (SDSDQ-8192, Bulk Package)
http://www.amazon.com/gp/product/B0012Y2LLE

Full story (note: I am a n810 newb): when I first entered this into my miniSD slot, I got the "Memory card corrupt or unformatted error". After some fruitless experimentation with my PC, I tried again. This time I pushed it in harder & it clicked into place. Obviously, the first time I didn't push it in far enough. Live & learn!