It's a free online wedding planner that is full of useful features like a budget planner to track payments, a guest list and RSVP tracker, and my favorite, the CHECKLIST! 
I love looking at the checklists on wedding planning websites to make sure I haven't forgotten anything. The best part is that on My Wedding Workbook, the checklist tasks can be added to your calendar, and you can receive email updates to remind you that you need to finalize your reception menu, for example. It's pretty sweet, so you should head on over to the website and try it for yourself!