I recently asked what the difference is between granting SELECT to a user (at a database level) and adding the user to the db_datareader role on StackExchange. The answer I got from RLF sent me to a link with some awesome charts showing how the various roles map to individual permissions. I realize that it’s a high level overview of the permissions and doesn’t display (for example) object level permissions, ie syssessions is only accessible by sysadmin. However it’s still an excellent reference tool. Personally I plan on printing out to put on my wall next to my DMV poster.