This Plugin gives you the possibility to hide the Dashboard before selected users. 
It is very flexible, since it works with an extra capability “Hide Dashboard”. 
This capability can be assigned to one or more roles and/or as an extra capability to one or more users.
Users with hidden Dashboard will be redirected to their profile-page.
You need also the “<a href="http://www.im-web-gefunden.de/wordpress-plugins/role-manager/" title="Role Manager Plugin for WordPress" rel="nofollow ugc">Role Manager Plugin</a>” for this Plugin.

IWG Hide Dashboard

"Hide Dashboard" hides the dashboard for all users with the capability "hide_dashboard".

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.

IWG Hide Dashboard vs Twitter Profile Field