bubbl.us is a web-based tool that lets you organize your thoughts and ideas into one coherent thought map.
If you've ever had a crazily detailed project assigned to you at work or school, you probably understand just how easy it is to accidentally mess up a step (or three!). bubbl.us is an online service that's here to help make things a little easier for you.
With an easy-to-use interface and a very quick account set-up process, you can really dive right into using bubbl.us in short order. From there, just start out with the first project you have in mind and go from there. Like most mind maps, bubbl.us starts you out with one thought bubble where you write your main idea (or perhaps a project title). It's reminiscent of quite few other mind mapping programs, the one difference being that bubbl.us is entirely web-based. You can essentially access it from any computer on the web.
bubbl.us even lets you share your mind maps and make them searchable for other users who might be looking for a similar map that's already been made. You can save individual maps for later use and even export to your heart's content.
The only real downside to bubbl.us is that sometimes the child bubble stems can be a bit hard to manage. You might end up making a sibling stem when you meant to make a child bubble. Fortunately, though, the undo button is only one click away. Some users might also find it annoying that using a mouse scroll ball tends to make your map zoom in and out instead of actually letting the page scroll.
For a simple and free web-based mind mapping tool, bubbl.us is pretty comprehensive.