[request] additional informations when a user signs up

I need an extension, where administrators can add and name own input-fields to the registration-form. Right now, there ist Username, Email, Email-Confirmation, Timezone and DST. I need further informations about my registred users, such as company or facebook-link.

The custom input-fields must be able to be flagged as 'required' and 'optional'. A title and a description for each field would be great:

Facebook: [..............] (required) - the URL to your facebook-profile
Company: [..............] (optional) - please fill in your company-name
Custom field x: [..............] (optional) - blah
Custom field y: [..............] (required) - blub
...

These infos have to be shown on the public profile-page. Each user must be able to edit these informations in his account. It's a great extension-idea, isn't it