Have you tried Spicynodes to make conept maps online?

Fresh from the oven and piping hot, SpicyNodes is limited only by your imagination. Entice visitors to explore and savor the experience of visiting your web site, add visualizations to your blog, create a mindmap or organizational chart, or encourage students to delve deeper.

Spicynodes makes it easy for students to create simple yet effective concept maps in minutes that look great and have a variety of content within them.

If you haven't tried spicynodes yet take a look it won't disappoint. Here is a link to what Spicy nodes can do.