FREE to-do list software

I've come to realize that if I don't write things down, I'll forget them. You should see my monitor. It's covered with little yellow sticky notes. If a strong wind comes along, my life is over and I might as well go home.
I just downloaded and tried something I want to share with you. Keep in mind, I'm running this on my Mac but it works on both Macs and PCs.
It's a little software program called "Doomi". I add something I need to remember to do, and I can even set a timer with the post. When it's time to remember to do my task, Doomi pops up from quietly sitting in the task bar and reminds me to do what I need to remember.
It downloads and runs with Adobe Air.
One of the reasons I like this program is because I don't have to add it to my already crowded calendar entries for more important items I store like meetings etc. and the fact that it sits quietly down in my task bar until there is something I need to remember to do. Then I get my message when I wanted to be reminded as shown of my desktop below.
Life is getting even better!