Dwarf Fortress labor preferences
tzenes answer is strictly correct. There is however no way in the game to see a list of all dwarves with a specific labor enabled (ie: mining). You must iterate through all your dwarves to check.
However, a custom utility called Dwarf Therapist has been written to allow you to do exactly what you want to do.
- Dwarf Therapist Forum/Info Page
- Dwarf Therapist Project/Download Page
- Select the dwarf, either through 'v' or 'c' and then choosing a dwarf.
- Select preferences ('p')
- Select labors ('l')
- Select the category of labor you want to change.
Its worth noting that currently selected labors will be highlighted, as will their categories.