I haven't tried it yet, but it looks promising:

http://pnotes.sourceforge.net/index.php?page=1

Looks interesting. Two somewhat similar web-based programs come to mind: http://www.myemailreminders.com/ and www.nudgemail.com . I especially like the latter as it works through e-mail, and I keep a dedicated account on my smartphone for my exclusive use. I also use Toodledo, but Nudgemail is pretty easy to push things off to a future time if needed. (I am a big fan of multiple reminders if you could not tell.)

--Ken