usb memory sticks and flash drives,the two most common used names for the devices,are used more and more these days instaed of the old floppy drives and zip disks which could only hold limited amounts of dat
the memory sticks now come in sizes of 256mb,512mb,1gb,2gb,4gb,8gb and some manufacturers even make 16gb models
i have found a 32GB USB Flash Drive Memory Stick + Ext Cable and Strap from http://cgi.ebay.co.uk/32GB-USB-Flash-Drive-Memory-Stick-Ext-Cable-and-Strap_W0QQitemZ130143954095QQihZ003QQcategoryZ108982QQcmdZViewItem,this is the biggest i have found,however with a pen drive this size you could in theory boot a operating system from one of these
however if you think that was big,take a look at this one....http://reviews.cnet.com/usb-flash-drives/kanguru-flash-drive-max/4505-3240_7-31829082.html,this is the Kanguru Flash Drive Max 64GB,a quality pen drive with amazing amounts of storage space
hope this helps
good luck friend!