A little while ago I covered the efforts of the "United Scripting Nerds" led by Rob Trew creating a scripted based solution to export OmniFocus data into a iThoughts HD MindMap, OPML and text files.
While it is a great solution the fact that a script is required may already turn some people away. Luckily the reverse workflow of getting a project designed in a mind mapping application such as MindNode Pro into OmniFocus is somewhat easier, as Eddie Sblack describes in his post.
Whether you use MindNode on the Mac or on your iPad the workflow will work as it leverages MindNode's OPML export capability. Other major mind mapping solutions like iThoughts HD also support this open standard.
Once you have a OPML file Eddie leverages OmniOutliner as an intermediate, not an inexpensive one, copying & pasting the entire Outline over into OmniFocus.