here is the deal -
It takes time to meet the Secure Digital (SD) standards, so to get the storage media out in a hurry -- they called it Transflash and left 'SD' out of the title.
Now that they've gotten their "SD" certification on it, transflash has been renamed "MicroSD".
You can buy a 512mb MicroSD card at BestBUy for about 60 dollars. I was at my local bestbuy the other day and they had about 20 in stock.
Do not get MicroSD and MiniSD confused, they are not the same. MicroSD is the EXACT same as Transflash though, 100% compatible.
i've got a 512 card that i use with a motorola e815.
www.howardforums.com tons of info on this stuff.
http://en.wikipedia.org/wiki/MicroSD_Card