Exactly. Todo lists are just flat files :) I use ~/TODO for this purpose.

I discovered this by trying to write my own TODO manager:

http://git.jrock.us/?p=doqueue.git;a=summary

After working on that for a while, I realized I just wanted a flat file :) Implementing the file was much faster than writing an entire application, I might add.

When I get some interest in working on this again, though, I will make a FUSE filesystem that gets the information from the web and makes a TODO file for you. Then you can use the web interface when you're at a different computer (or you want to share TODOs with a friend), and the file otherwise. It might be interesting.