This way the files are available whenever I switch computers and they are automatically backed up.
I keep several text files in a directory:
1. A backlog. This is roughly similar to a scrum backlog. It's disorganized and needs to be, because it's important that I can easily put stuff in here when an idea comes to me without having to get distracted organizing things.
2. A plan. I periodically select a few things fro mthe backlog and organize them into a chunk of work that I plan on doing next. I put checkboxes like this [ ] next to each item, and when I finish the item, I change it to this [x]. The item that I am currently working on looks like this [.] to indicate it's in progress. That way when I get interrupted for 2 hours or a day and come back, I can easily see what I was doing and get back in the groove.
Periodically I move everything I have completed from the plan text file into a file like history/2012-12.txt. I put a date right before the items I put in. This way I can go back and see what I completed on a given time period.
Also into the plan file I will put notes of issues I'm researching, which can occasionally be useful to go back and look at a month or more later. Those notes get moved into the history file when that chunk of work gets completed.
The benefit of this approach is that I can use this method even when I am traveling on the train, and it let's me easily switch computers and keep working. I find my to do list to be just as important as my code, because it's very hard for me to be productive on a large project without continuous planning.