Evernote (App Store) is brilliant. There is also a Mac and PC app available as well, and a web portal, and they all stay completely in sync - over the air. It's perfect. You can put in text notes, audio notes and photo notes. On the Mac app, you can also take a very clever screenshot using the quick toolbar icon. Everything is logged as a note, or to do.
If you're into your GTD (Getting Things Done), you should take a look at Things (also in the App Store). It currently doesn't sync with the desktop version of the app, but it will do very soon. I love it. It's such an uncluttered way of dealing with your tasks.
Also reQall (also in the App Store) is really very neat. It's got some pretty impressive technology behind it as well which will impress even the most unimpressable (is that a real word?!). You can either post to do's in the old fashion way (typing them in) OR... you can press a button to DICTATE your notes. It's uploaded to their servers, they crunch your audio clip, and then it comes back into your To Do inbox shortly after as a text item. There's also US and UK freephone/geographical numbers to be able to call up from anywhere and dictate your message too.
No doubt Apple will do something like this in three years time and everyone will say "oh wow, isn't this great"
Give up on Apple implementing To Do's properly in Leopard/iPhone. It's clearly incredibly difficult to conceptualise and implement.