I have finally found a great tool, bubbl.us, to use as an alternative to Mindmeister. Both programs are great for mapping out ideas. With bubbl.us, however, no paid membership is required. On the downside, bubbl.us does not possess the sharing capabilities of Mindmeister. I encourage you to try out both. Check out this tutorial on bubbl.us to figure out which one works best for you!
To find out more information on Mindmeister, read an analysis by Megan Pearce on her blog here.