Testing a microSD to memory stick pro duo adapter from Dealextreme on a PSP 3010 (firmware 6.35 PRO-B4). If you intend to use it on PSP, you will need to format the micro SD on the PSP ("System Settings" -> "Format Memory Stick"). Formating it on PC didn't work.

MicroSD to Memory Stick Pro Duo Adapter:
http://www.dealextreme.com/p/sdhc-microsd-transflash-tf-to-memory-stick-pro-duo-adapter-converter-16gb-max-17789?r=46828650

16GB MicroSD (class 4):
http://www.dealextreme.com/p/designer-s-micro-sdhc-tf-memory-card-16gb-class-4-50569?r=46828650