If you have accidentally formatted your USB drive, you can use these tools to recover their data -
PC Inspector File Recovery - If you have a USB drive running FAT 16/32 and NTFS file systems, this software should fit the bill. One of its main advantages is that it recovers the file along with its original time and date stamp. It supports data recovery from drives with damaged boot sectors which is the most common reason for losing your data. The developers page is available only in german but the software is multilingual and you can set its language to english.
Restoration - This lightweight application does not require installation and functions well as a portable recovery tool. It allows you to restore data from a formatted USB drive. You can choose to filter specified file types to be scanned before recovery. For example if you only want to recover some deleted images you can recover files having a.JPG extension and have the software ignore the rest.