You can use the 'remote command' and 'remote login' commands to attach to the SP of the Supervisor or any DFC equipped modules.

http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst6500/ios/12.1E/native/command/reference/R1.html#wpxref41123

The SP supports some of the usual 'show' commands, plus other stuff that isn't available on the RP such as test etherchannel:

http://www.cisco.com/en/US/partner/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

I can't seem to find a list of supported commands on the SP but I assume '?' still works? I haven't got access to a 6500 to test.

HTH

Andy