On a Linux Web Server:
To extra some files rather than everything
tar -xvzf website_archive.tgz home/username/thefolder
If the archive is huge it will still take time to extract the folder/file. But it is better than untar everything.
To list the content of a gz tar ball
tar -ztvf website_archive.tgz
To list content of the bzip tar ball
tar -jtvf website_archive.tar.bz2