Portable software for the Posix world

Is there any "portable" software for Linux (i.e., Ones that can just be un-tar'd and used, instead of in rpm, or similar format. to be used in conjunction with a package manager)? Also, are there any caveats to this that don't exist for Windows portable programs?


P.S Not sure what the community thinks about adding the tags like [tag:portable] or [tag:no-install] to this site is. I realise that Portable is likely to be considered more of a Windows feature, but would think that software that doesn't come in a rpm format, or via a repository, may be loosely considered as such in the Posix world.