Portable Freeware Applications 
http://www.portablefreeware.com/all.php (PC Applications) 
http://www.freesmug.org/portableapps (Macintosh Applications) 
 
These sites gives you a categorized list of hundreds of freeware programs that "can be extracted to any directory and run independently without prior installation." This means these programs can be installed on a USB flash drive or flash memory card, burned to a CD-R, and copied from PC to PC by simply copying the files.