Adding textboxes dynamically as needed

I want users to start with one textbox and then add additional ones as needed.... this will be used on one scenario for email addresses and another for license keys as an example of usage.

So they add their first email address, with validation. Then below it is a link:
+ Add Another Email Address

Then finally the [Submit] button.

On press of the Add Another Email address, another box appears and so forth until they have all they need.

I have searched the internet and only found one bit of source code on it. It's close, but has some problems and is klunky.
<link to competing site deleted by COBOLdinosaur, Topic Advisor>

I also found this, but it's not pretty:
http://viralpatel.net/blogs/dynamic-add-textbox-input-button-radio-element-html-javascript/

I want it to say:
Email Address: [textbox]
[with validation]

Does anyone have any better suggestions for how to do this and how to read back the data on Submit? I don't care if it's asp.net or javascript as long as it's instant and works well. And I can create it and retrieve the results easily.

thanks!