PQI, a company in Taiwan has developed the world's slimmest flash drive - the PQI U510. 

This credit-card sized drive can hold upto 16 GB of data!

It is compatible with Windows and Mac and has a retractable USB cord inside.  You can transfer data at high speed, since this drive supports USB 2.0.

The 'card' drive measures 85 x 54 x 3 mm.

[via]