If you are a "do it yourself" bride, a number of free tools are available.
If you have used a Google Doc, you will find these incredibly easy to use. These are nice because they are stored online- and you can allow others helping to plan your wedding access to these documents. The changes are then made in real-time...so there is no more emailing your guest list back and forth with your mother-in-law.
If you have a smart phone, you most likely have access to a Google Doc "app" in which you can access and update your data on-the-go.
This technology does not replace the skills of a wedding planner, but it is a great option for people that are looking to take care of things themselves.