Gmail doesn't usually open up the CC: or BCC: fields until you've clicked the links to make it so, but hitting the "d" key opens up a composition window with a CC: field available, while "b ...

Gmail users with Firefox and Greasemonkey: If you often use the CC or BCC field in Gmail but you're sick of clicking on the "Add CC" and "Add BCC" link to do so, we've got a pair of user scripts ...