Text2Mindmap simple and easy to use; allows you to outline your ideas and draw a map from indented text. Bit limited (no notes, links, cross-node links)
Coggle - requires Google login. Allows drag and drop of formatted (indented) text to create a map. Seems limited (no notes, links, cross-node links)
WiseMapping - free, seems pretty full featured; no apparent limits.
Mindmeister - limited to three maps for free account. Revert change requires premium account
