The following comes from the Aggie Catholics site:
2. It is the ordinary way to have our sins forgiven.
3. We receive grace to resist sin through the Sacrament, as well as forgiveness.
4. We learn humility by having to confess to another person.
5. There is built-in accountability.
6. Our relationship with the rest of the Church is healed.
7. We receive counsel from the priest.
8. We can be comforted hearing the words of absolution.
9. All are sins are wiped away.
10. Helps give you the strength to forgive others.
11. It doesn't cost anything.
12. We may not be positive that we have "perfect" contrition without it.
13. Helps us go deep within and think about how we can improve.
14. It feels good emotionally.
15. When we realize (again) we are sinners, it is easier to be patient with others.
16. Always confidential - what is said in the confessional stays in the confessional.
17. No more guilt.
18. We are better prepared to receive the Eucharist.
19. Forgiveness is a necessary part of growing in holiness.
20. Our consciences can be better formed.
21. If we have mortally sinned, then Confession brings us back into the family of God - The Church as well as restores sanctifying grace in our souls!