The Causes application on facebook uses dynamic pop-ups with tips while filling the form to create a new cause. Nice implementation.

I really enjoyed the mint.com account creation page.

Here’s why:

1. It gave me feedback as I was working through it (filling out each field correctly was “rewarded” with a green OK icon). 

2. Unobtrusive marketing text on the right — it didn’t feel overwhelming, but I could have read it if I really cared.

3. Simple and light look and feel.