Producteev’s pricing plan offers quite a bit of freedom for personal users (2 users per workspace and 500MB, I believe) — and personal workspaces are free.
If you love Evernote, I would suggest you use it for your reference and delete any attached images and files in Producteev that are no longer needed (completed tasks and such). 500MB is a fair bit of space for documents — and you could always attach an Evernote/Dropbox/Box.net/Google Docs share link to the note instead of the actual file.
Where you will run into cash outside of this is in collaborative teams in a workspace. Which is still pretty reasonable, and only needs to be active as long as the collaboration of more than two people are needed.
Hope that helps! :D