These sites cover all of the "major" citation styles.
Need help with the writing process?
The Cal U Writing Center provides free consultations and guidance to Cal U students, staff and faculty. They help people of all skill levels and at all stages of the writing process. The center provides individual conferences with trained writing consultants, group workshops and the Writer's Hotline.
These tools let you chose your citation style and source type, then you enter the information and they create a formatted citation for you.
NOTE: These can be very handy, but be sure to check your results for errors! Automation is not perfect!
These resources go beyond citations to cover writing process in general--and annotated bibliographies in particular.