From the ls(1) man page on Mac OS 10.6.1:
If the file or directory has extended attributes, the permissions field printed by the -l option is followed by a '@' character. Otherwise, if the file or directory has extended security information (such as an access control list), the permissions field printed by the -l option is followed by a '+' character.
From the available options list:
-@ Display extended attribute keys and sizes in long (-l) output.
-e Print the Access Control List (ACL) associated with the file, if present, in long (-l) output.
These will let you see the value of those extended options. FWIW, ACL info can be set using the same chmod(1) utility you are probably already aware of. :-)
There doesn't appear to be an easy way from the command line to do anything with extended attributes.