I use http://workflowy.com/ http://workflowy.com/ In short it's a tree with potentially infinite depth, search, tags (#work) and contacts (@mummy), and the abi

I use http://workflowy.com/ http://workflowy.com/ In short it's a tree with potentially infinite depth, search, tags (#work) and contacts (@mummy), and the ability to change the root of the tree. It's also possible to share nodes in read or read/write with other users. It's exportable to Markdown and other formats. Sadly Collate notes nor Workflowy are free software (as in libre), and I cannot install them on my server :-(