I've been trying to find a good way to have a simple todo list that is editable on the web, on my Mac, and on my iPhone.
I've been looking at the apps coming in to the App Store, but none of them seemed really worth the effort, especially since they don't have anything that works on the web or on my Mac.
I tried Evernote, but the dumb thing doesn't let you edit entries created on the Mac on the iPhone when you're offline (which I am a lot, because I don't have a data plan, just wifi and T-Mobile pay-as-you-go). It doesn't matter if you "favorite" them, it doesn't work because the Mac-created entries are created with rich text, which can't be overriden (e.g. you can't use simple ASCII text). There was even a todo list on the market that costs 50 friggin' dollars plus $10 for their iPhone app. TODO: fuggetaboutit.
But wait: Address Book contacts have a notes field. And I just found out you can synchronize Address Book with Google Contacts, and that Google Contacts has its own URL so you don't have to go through Gmail.
Problem solved. I create a contact called Todo, and in the notes field I put all my action items. I can even categorize if I want multiple todos (Todo-Family, etc.) but I've noticed that becomes too complex and is a good reason for me to slowly stop using it, and that defeats the purpose.
Now I can edit that note in Address Book on my Mac, on my iPhone, and even on the web if need be. That works for me.