using tar

[yahootintin.11730620 at bloglines.com]

hi,

i'm using tar to gzip some directories like this:
  tar cvzf ~/foo.tar.gz
/foo

this tars everything in the foo directory.  but i want it to tar everything
in the foo directory except for the bar subdirectory (eg. /foo/bar).  i've
looked at the man pages and can't figure out how the exclude flag works.

thanks.