emillion and AW seems to have the best source of li-ion cells. I recently purchased two AAA li-ion + nano charger for $12.
Emillion has killer 750 mah cells for $4 ea. these actually measure at aprox. 600 mah, but are better than anything else used so far. the 700 mah version tested out slightly better.
Wei just posted a feeler for some killer looking li-ion cells deals