Excellent Dynamics

Adds additional meta fields for User Profile and link on author page in widget “Recent Comments”
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Lotos Author Fields

This plugin adds additional fields in user info.

Jesper Johansen (jayjdk)

Twitter Profile Field is a simple WordPress plugin that gives the user a new field in the profile page to add in their Twitter username.
The pluhin also provides a shortcode which allows authors to display their, or others, Twitter usernames, optionally with a link, in posts, pages, and text widgets.

Twitter Profile Field

Adds an additional field to the user profile page where the user can enter their Twitter username.

Lotos Author Fields vs Twitter Profile Field