Google Calendar is good for recurring stuff. It emails me reminders and I have text notifications setup for more important stuff. I've actually got a monthly reminder to do DB maintenance for my sites. That's how lame I am.
For quick stuff I've been using Google Tasks. Which is pretty cool it's got a nice mobile interface too.
When I'm out and and about and remember something I need to do at home, I text my email address.
Pretty much all reminders center around email which is where I always am.