how do I verify that the the checksum is correct?

[Anthony Bryan]

If you're just talking about verifying the checksum of the ISOs, you
can use a Metalink to download them. They're XML files with all the
mirrors and checksums. Once the download is done, it will
automatically verify the checksums. Usually much faster too.

To install:
yum install aria2

To use:

aria2c URL
or
aria2c http://download.packages.ro/metalink/fedora/FC-6-i386-DVD_iso.metalink
etc

The .metalinks for Fedora are at http://download.packages.ro/metalink/fedora/
-- 
(( Anthony Bryan
  )) Metalink [ http://www.metalinker.org ]