If you're on a Mac, you could try OmniFocus. It's a pretty decent implementation of Getting Things Done (the core of which is what you're describing). I've been using it since it was in beta and I'm really happy with it.

It lets you make folders, projects, and actions. Actions can have start/end dates, repetitions, and contexts. The idea of contexts is that you should be able to see what actions are available to you at any time in any place. Actions can have sub-actions and you can specify whether the sub-actions have to be done in sequence or can be done concurrently. You can also set up a global quick-entry hotkey which will let you enter an action and have it placed in your Inbox so you can organize it later.

There's also an iphone app, but I haven't found it teribly useful. OmniFocus has the ability to grab tasks from Mail.app in a special (user-defined) format and I found that works as well for adding new tasks as anything.

The downside is that it's $80. I got it for $40 when it was in beta, and I think it's a much harder sell at $80. If you aren't interested in this, or aren't on a mac, just google "getting things done" or "GTD"

How about Tracks? http://getontracks.org/

It's also based on the GTD philosophy, it's very easy to use and has some nice features. You can find an online version here, try the demo first to see if you like it: https://tracks.tra.in

If you're on a Mac, get Things.

http://culturedcode.com/things/

Beautiful software, incredibly easy. I can't deal with get-things-done software, but if I had to use a program, this would be the one I used.

Just to further clarify what I want, I like to break tasks down so that I'm constantly working on the "Next possible logical step" no matter how small.

Most of the time I just write them in a list in a text editor, but then i get to the point where i need to clear out my scratchpad - thus losing track of my progress.

Obviously seeing my progress in a chart/graph is not necessary to get stuff done but it might help with motivation :)

It's not a web app, but I highly recommend OmniFocus for mac and iphone. The desktop app and iphone app can sync with each other, which is nice. I use it all the time, and it's great for doing brain dumps, then organizing projects and todos.

I use GTD tiddly wiki. And I wrote about it on my blog http://chanux.wordpress.com/category/computinglife/

Saw this - http://www.joesgoals.com/. I have not used it before. Why not try it out and let us know?

If you're an Emacs user, I suggest the Org Mode package.

GoalEnforcer is great visual goal setting software (way easier to use than "lists"), but they don't have a web based version yet. They have both Windows and Mac versions and you can store your goals locally or on the web (using the built-in ftp)

You mentioned "I like to break tasks down" and " Obviously seeing my progress in a chart/graph ... might help with motivation" I can guarantee you'll love this software. http://www.goalenforcer.com Check the free demo. This tool is so easy and fun to use that it fells like you are playing a video game.

I've been experimenting with gmail and tags but it's not much better than just using a spreadsheet at the moment.