[cbenz]

I use 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 :-(

[NickBusey]

Shameless plug: I am currently working on a free (as in libre) Workflowy replacement. https://github.com/NickBusey/BulletNotes

[zaphods-towel]

Awesome, thanks for sharing!