Portable apps are a great way to carry programs on your USB pen drive or for using them without install. I recently mentioned them in the 10 steps to prettier, more useful and secure USB pen drive If you like portable apps (which I very much do) then I suggest you have a look at TinyApps.org. The site has a list of applications that are.. um.. "tiny". All the applications listed here are small in size but not in their usability and advantages. It lists some of my favorite softwares like IrfanView, IconShop, Easy Thumbnails, Lynx for windows (very useful text based web browser), PuTTY, Locate and many more useful softwares.
The apps listed are generally free and some of them are portable (means they don’t require install), while some applications are shareware. The whole idea is to have apps less than 1.44MB (size of a standard floppy, although these are almost obsolete). Still I mention the site because some of the apps are actually command based and thus can be used in batch files to perform certain functions that are not possible on the Windows command line by default like web-browsing of secure logins. Another good use is to keep these apps on a USB thumb/pen drive, that way you can have a lot many tools without using too much space.