Recently I decided that it would be useful to use a task manager. Several of my colleagues are using Remember the Milk and I decided to join them, since then we can share tasks when needed.
I was really impressed with the signup process. It makes sensible use of technology to tell the user whether the text they have input is correct for the field as the user fills it in. This is better than the user being sent to a check page, since it is often difficult to choose a unique username.
Also, a few months ago I was signing up on a site which used a different method for asking the user for his or her time zone. Rather than directly asking for the time zone it presented the user with a list of current times and asked for the correct one to be selected.