This is very dependant on the modules you have in your 6500 chassis and also what features you are looking for eg IOS modularity.
Cisco release "Safe Harbor" versions of code for the 6500. Note the spelling of Harbor - if you are English like me then you can spend a failr amount of time mistakenly looking for "Safe Harbour" :-).
These Safe harbor code versions are kind of like the equivalent GD code releases you get for IOS on routers. The following link is a good place to start.
http://www.cisco.com/en/US/netsol/ns504/networking_solutions_program_category_home.html
Jon
