For personal to-do lists, I use http://www.toodledo.com/ http://www.toodledo.com/ which is great for having many options (occur every month, every 2 weeks, last

For personal to-do lists, I use http://www.toodledo.com/ http://www.toodledo.com/ which is great for having many options (occur every month, every 2 weeks, last Wednesday of the month, etc.), and syncs between mobile and web. For work, I basically use pen and paper or slack reminders or self chat.