Ever since getting an iPhone this has been an issue. Prior to this I had a palm pilot and did essentially what David Allen even said which is just using notes. Set a different category for each of your contexts and each note is a new task. Worked great. I could reorder tasks as I needed, reassign to different contexts by changing the category, etc. Then I go to the notes in the iPhone and seriously disappointed in how featureless it is. If it had two things that I figured would be pretty obvious I would be happy. A way to reorder notes (right now it just puts the most recently edited at the top). A way to categorize notes (even if you want to give it a more hip name like "tag"). Without those it's been so hard to use. I've tried just making a note with the title being the context, but it's still just been a struggle to use.

As far as web-based GTD, I like http://nozbe.com/)">http://inozbe.com/[/url] (which is the iphone version of [url]http://nozbe.com/). It's rather limited in the free edition (5 projects max, can add 1 context aside from the 10 or so they give you) but it works nicely.

The thing that I don't like about web apps for things like this is when it comes to tasks and either adding or removing things, I want access to it NOW. I don't want to wait for a page to load, especially over edge. Then navigate through some menus, inozbe doesn't remember your login info so you would have to constantly log in, etc. If I need to add something, I want to get to a note pad and type it out and get back to doing stuff asap. Same thing when I finish something. And then those rare occasions you don't have a connection, you have no access.

In case I didn't make my point big enough, I don't use nozbe or any other web apps for this :) . Right now I just struggle with notes on the iphone. I still carry my palm pilot around because of some apps on there I still use and because of the notepad. I really hope they do some improvement over the notes app.