Another tool that is quite useful but that I have to look up the syntax is GNU tar. In short:
To create an archive:
tar -cvf files.tar fred joe simon will put the files fred, joe and simon into a tar file called files.tar.
To extract an archive
tar -xvf files.tar will extract,
tar -xf files.tar will extract them without telling you lots about it. Finally
tar -zxf files.tar.gz will uncompress a gzipped file.