Rackspace cloudsite enable GZIP compression

<IfModule mod_deflate.c>
  # Insert filter
  SetOutputFilter DEFLATE

  # Don't compress images
  SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary

  # Make sure proxies don't deliver the wrong content
  Header append Vary User-Agent env=!dont-vary
</IfModule>

curl -I --compress http://www.example.org

If it did work the output will include Content-Encoding: gzip.