Here are posts removed from PortableAppZ (notified to Blogger to infringe upon the copyrights of others).
Take a “snapshot” of anything on your PC screen without installation.
Download Portable Snagit 12 Online (0.2 MB) 28/10/14
In first screen enter: 1241
For Windows XP: Download Portable Snagit 11 Online (0.2 MB) 12/02/14
In first screen enter: 1143
Extract and run SnagitPortable.
Don't forget to close if in systray when leaving.
Output set in Snagit (at the root of portable folder). If you want to fix paths yourself edit SnagitPortable.ini.
Settings of installed Snagit should be preserved.