Today I would like to talk about Portable Apps. Portable apps are softwares that do not modify the registry of the computer; all the required resources are contained inside of a single folder. It can for example be launched from a USB drive.
A number of portable apps can also be launched without admin permission (not all of them though). You can for example launch
- torrent software such as utorrent,
- Image editor such as Gimp or Inkscape,
- Media player such as VLC,
- 3D modeling software such as Blender,
- Open Office
- etc.
Many of those softwares are available on portableapps.com. Coupled with a persistent live OS on USB key, it makes the perfect traveller key.
The nice thing with portableapps.com is that you can install the launcher, that looks just like a secondary start menu, on a USB key and use all the apps available on portableapps.com from there. It appears just like the Windows start menu on the right of the desktop. 
Another great website with portable apps: pendriveapps
It is also good to know that some non-free softwares have their own portable version. This is for example the case for Microsoft Office, Adobe Photoshop or Nero Burning ROM.
Here are a couple of other usefull portable apps that are not available with portableapps.com suite:
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