The following options are available out of the box under Site Settings > Site collection audit settings:
Documents and Items
- Opening or downloading documents,
viewing items in lists, or viewing
item properties
- Editing items
- Checking out or checking in items
- Moving or copying items to another
location in the site
- Deleting or restoring items
Lists, Libraries, and Sites
- Editing content types and columns
- Searching site content
- Editing users and permissions
The last option, Editing users and permissions, might get you what you want for users.