I currently have the these portable apps installed on my key: FirefoxPortable (it's amazing that this app can be updated like if it were installed on the PC), Notepad++Portable (my favorite text editor with multiple plugins and syntax highlight for almost every programming language), TeraCopy (for large file copy,move), Open Office (useful when I have to open a Word file in a computer that has not MS office at all) and PidginPortable (useful when need to chat in computers that are not mine XD).