Always in the Pandora:
2x 32GB SDHC (Transcend class 10) - FAT32
+
Samsung S1 250GB 1.8'' USB hard drive (small!) - NTFS
16GB USB key - FAT32
The harddrive is great for putting my large music library, some extra playstation cd image, backup of the 2 SD card, videos...
It's really great to be able to just plug the harddrive into the Pandora. Last time I was copying large files from the harddrive to the Pandora SDCARD. It's a bit slow on lot's of small files but the speed is still pretty decent.
The battery life does take a large hit as expected but I think it was still showing something like 4h battery life left with the screen on while copying... that's pretty impressive !