Pros: Easy to use mindmapping tool; Allows combination of text, drawings and photos; Free
Cons: Limited to one board (map) at a time
Buying Advice: Don't want to drop fifty bucks on Omnigraffle? Play with popplet lite for free, instead, and hope that support for multiple projects comes in the next version. And soon. As is, it's a great - if limited - app.
Like I said in my review of Pocket Note iP3:
I'm really excited about the prospects of using iPad as a brainstorming/mind-mapping/whiteboarding tool ... I've been spending a few bucks and lots of time trying out some of the free and inexpensive apps that look like they might give me what I need to get my thoughts in order, iPad style. Two of the most intriguing options I've found so far are Pocket Note iP3 and popplet lite.
Pocket Note is a sort of digital journal/scrapbook meets whiteboarding meets idea organizer app. popplet lite, on the other hand, is a more traditional mindmapping app. Mindmapping is like flowcharting: You make a "Popplet" (resizable rectangle), write or draw or drop a photo in it, and then connect it to other shapes. As mentioned above, Omnigraffle is one of the premiere mindmapping tools out there, but it costs $49.99 in iPad form. Popplet Lite is free, attractive, easy to use, and lets you create a single, never-ending mindmap on your iPad. I particularly liked its clean look and light, functional, easy to learn UI.
The problem with popplet lite is that you're limited to that one, single, never-ending mindmap. There's no way to save your work and start anew - you have to wipe the slate clean, permanently, if you want to start over. Yes you can "save" your mindmap to your photo library, but you won't be able to pull it back into popplet for editing later. Aside from that one (enormous) issue, popplet works pretty well.
Since this is only version 1.1.1, and the "lite" moniker would lead one to believe that there will be a paid "premium" version in the works, I have faith that revisions of popplet are soon forthcoming. Hopefully they'll address some of my concerns while also adding other nifty functionality. As it is, popplet lite is a handy app for working out notes and ideas on your iPad, so long as you don't mind keeping tabs on everything on one giant board full of popplets.