From time to time, I've had the need to extract a single file from a tar archive. How to do so is pretty poorly documented in the man page, but it's actually easy to do. If you have a tarball named "my.tar" with a group of files in it, and you want to extract "hello.txt", you would do the following:
tar -x hello.txt -vf my.tar
Before I extract anything from a tarball, I always preview it's contents to avoid "tarbombs" (tarballs that extract directly into the CWD).
tar -tvf my.tar
Or if it's gzipped:
tar tzvf my.tar.gz
Lastly, newer versions of Vim can browse a tarball out of the box and open any file contained within.
vim my.tar (displays a file browser)