Looking for suggestion: Powerfull, opensource wysiwyg

Anyone have any good suggestions on wysiwyg editors? This is for people who arent computer experts, so I want to simple enough.

It needs to be:
- Powerful enough to give them good control
- Ability to add/delete images

Ive already seen a few. CKEditor editor looks promising.

Note: the editor will only be altering part of the page (the layout is being built around it).

Anyone got any suggestions?

edit: And it needs to be free (website for non profit organization)

tinyMCE