Use a third-party CSS or JS Framework, a self-hosted service like a CRM, or a third-party service with the site.
Provide a simplenews newsletter subscription pane for the ubercart checkout.
This module provides a simple field for handling Twitter username, which can be added to content types for validating and storing a Twitter username.
Zoho is a drupal module which provides an api to connect with Zoho CRM.
Commerce NAB Transact is a payment gateway module for Drupal Commerce that currently allows you to process credit card payments on your site using NAB Transact's XML API payment service.
Clone of http://drupal.org/project/referralsources to implement some fixes and improvements.