As Twitter are about to stop allowing use of Basic Auth I have updated the Twitter friends timeline web part to use OAuth.
When you add the web part to the page you will be directed to the Twitter OAuth login page once. After that the authentication token and secret are persisted in the properties of the web part although only the token is browsable.
To change the account being displayed simply clear the Token property in the Miscellaneous section of the web part properties and you will be prompted for a new set of credentials.
As a bonus I have also included a Twitter search web part. This does not require authentication but does require you to provide a search term in the Miscellaneous section of the web part properties.
To download the .wsp SharePoint solution file visit this page.
Thanks to Shannon Whitley for his OAuth Twitter example