Popplet is a great service that combines the best of online sticky note services like Wallwisher with collaborative mind mapping functions. Popplet allows you to create a wall of multimedia sticky notes that you can share with others. Your stickies can include videos and images that you pull from other online services.
The mind mapping element of Popplet is the option to connect your notes. To do this just click one of the small circles that hovers near your note (Popplet calls them “Popples”) while you’re editing. Click those small circles will launch a connected blank note that you can edit. Popplet is available for iPads.