www.mindmeister.com is one option. There is a new feature in Mindmeister that allows you to send emails to your mind-map application. This might allow for quicker and easier additions to a mind map there.

I use Mindmeister all the time, though I have found that it works better on a laptop than on my N800.

There ought to be a whole series of web sites such as Mindmeister that have web apps that work REALLY WELL for the N800/N810. Where are they? Most of the ones I use just barely work for my tablet, which isn't quite good enough.

(Though I have found that Notecase makes a pretty good substitute for mind mapping in a pinch...)

I'll try labyrinth when it supports a virtual keyboard -- my understanding is that the current version does not.