1. Mini Operating systems Yeah!! You can carry a portable operating system on your pen drive which will help you log into any PC with your own password and fix the crashes. There is a long list of available options though it will invariably be a flavor of Linux. To make your job easier I would recommend a visit to pendrivelinux.com and here.
2. Virtual Machine You can turn your pen drive into a virtual PC by installing portable virtualization softwares like Mojopac. It will help you carry your files and softwares with ease.
3. Security on the move There are a host of security related applications that can fit in your pen drive and thus travel with you. Thus your data will always be secured whether or not the host PC has an anti-virus or spam guard. Avast Virus Cleaner, ClamWin, and McAfee Avert Stinger are some of my recommendations.
4. Portable Applications Virtually every software today has a portable counterpart. Right from web development to design to messengers to games, there is nothing that is not available in the portable form. You can stuff some of these in your pen drive and work on the move without actually having to carry your laptop everywhere. One can get a whole list of such applications and details on pendriveapps.com or portableapps.com.
5. Value addition There are certain applications which if installed on the pen drive can help it serve you better. These are thus value addition softwares. Pendrive.com lists a few of themhere while Snapfiles offers these. For data recovery from a pen drive, one can go for applications like Pro data Doctor or Memory stick data Recovery or Restoration.