A friend of mine and a skilled developer, Marc-Antoine Ross from DevTaxi, did a great review of Web 2.0 forms and I think it's worth reading! So here it goes:

I decided to review the registration forms from most of the sites that made it to the invaluable Web 2.0 Awards.

Most of the registration forms were very disappointing.

• Some will validate on submit, but will display very unclear messaging to the user when an error occurred
• Some look like an entry form to the FBI (Yahoo!)
• Some display the password in clear text in the form!
• Most of the registration forms had no JavaScript / AJAX validation at all.

My Recommendations

• What can be validated through JavaScript should be done on submit or on change (email, password match, password strength)
• What can be validated through AJAX (username availability, email already registered) is a nice to have
• On submit, all errors will be reported at once with invalid fields highlighted, instead of stopping after each error found
• Each field's requirements should be displayed near the field
• Focus should be clearly changed to inform the user of the error to be corrected (focus to the first error found in the form)
• Error messages should be clearly visible. Different colors for errors than positive feedback. Feedback containers should be positioned in such a way the form doesn’t shift down when messages are changed.
• An input’s background and border color should be changed (to red) on error and its border to bold when focused.
• Terms should be "Sign in" and "Register". I find "Sign in" and "Sign up" too confusing. Where do I start again? Oh, that X at the top right
• Use labels in your forms!

A Few Good Examples:

1.Validates inputs on change, suggests improvements / errors.  Not visually attractive.

• http://blummy.com/register.php
• http://www.newsvine.com/_tools/new/user

2.Simple and efficient

• http://looklater.com/do/createaccount
• http://eventful.com/register

3.Nicely designed, good level of feedback to the user

• https://secure.fluxiom.com/signup/private

4.I like the information provided to the user for each input

• http://multiply.com/user/join/

Again, thanks Marc-Antoine. Do you guys have any other recommendations or suggestions?