If you have direct access to your WordPress database, you could use a tool like PHPMyAdmin or HeidiSQL to query the post and user tables and extract the information you need from the appropriate tables.
I discuss how an SQL query is constructed to get specific categories in Does WordPress Offer A Way to Get only Child Categories?. You can probably construct your own query to get the needed information with some time.
Or, you could take the simple option and install something like Export 2 Excel.