How to Securely Delete Data from Phone and Card I'm planning on selling my current Android (2.2) device and was wondering what is the best way to remove all of my data from the phone and memory card. Will a factory reset do it? What about formatting the card?
Erasing your phone internal memory

I have not tried it but using Android fastboot or an recovery ROM it should be possible to overwrite each partition on your device. Fastboot also supports an erase command - I assume that this erase can not be considered a secure erase. 

Therefore a secure way would be to overwrite to the two partitions userdata and cache (and may be others depending on your device). The image used for overwriting should be as large as the partition.

Erasing the SD-Card

SD-cards can easily be "undelete" using a card reader and a common PC. Therefore it is strongly recommended to wipe it. 

Best way would be to use an SD-Card reader on your PC and then use a tool like WipeDisk.