Social Circle
One of my friends wrote a cool app to manage cyclical to-do lists called Social Circle. It’s for stuff you want to do on a periodic basis. For example, you could use it to remind yourself to keep in touch with longer distance friends or relatives.
At work, a group of us use it to keep a list of places we goes to lunch — that way we can keep track of places we haven’t been to in a while. You can also use it to keep track of weekly chores and such. Check it out!