Userscripts.org

Display several informations about the twitter profile your looking at to help you decide wether or not s/he's worth following

Add toggles for showing/hiding @replies and #hashtags on twitter.com and brizzly.com

Enable replies (of a sort) to one or more tumblr dashboard notifications (click the notification icon)

Go directly to a post on your dashboard so you can reply!

Always set the "Let people photo reply" checkbox when making a new post

This userscripts adds a replies link to all twitter profile pages.

This script is no longer valid. Shows replies to a user in the sidebar of that user's Twitter page

Adds a "Last Page" link to topics in deviantART's forums.

Allows “in_reply_to_status_id” and “source” fields to be modified directly.

A simple script that displays the number of unread @replies and adds a Mentions tab in the Twitter sidebar.

Add smilies to replies on userscripts.org. The buttons add the selected smilie into the reply text area.

The buttons add the tags into the reply area around the selected text.