CamTwist is a software package that lets you add special effects to your video chats. It's also possible to stream your desktop and still images. With CamTwist, you can also use multiple video chat programs at the same time.
(commercial) ChatFX brings visual effects to iChat that are practical but also incredibly fun.
Chax is a collection of minor modifications and additions that make using Apple's iChat more enjoyable.
ChitChat (formerly WhatsMac) is a Mac app wrapper around WhatsApp's web client, WhatsApp Web.
DMTool is a DSL Modem Tool for the Siemens ADSL2 Modem.
FrostWire is a community driven project based on source code released by LimeWire LLC to create and maintain a Gnutella client according to the open standards of an international community.
GLoarbLine is a feature-rich, stable, safe and free client and server suite based upon the GNU General Public Licensed "Openline" source code.
Featuring a three-dimensional view, iChat AV 3 for Tiger practically puts your colleagues in the room with you, making it easier to follow the conversation. View their faces reflected into space, just as if they were sitting around a conference-room table.
iiUsage is an usage meter for iiNet, an ISP in Australia. It displays your volume usage information in the menu bar.
(commercial) ImageCaster allows you to take virtually any image - from video camera or other sources - and broadcast it on the internet or store it locally.
Internet Connection Keeper
Internet Connection Keeper allows you to keep your internet connection alive so that your internet provider does not disconnect you.
Internet Disconnector allows you to automatically close your internet connection after idle time and put your computer to sleep.
Internet Reconnector allows you to automatically reconnect your internet connection when it disconnects.
MChat is a simple chat application.
Messenger for Desktop
Messenger for Desktop is a simple & beautiful app for Facebook Messenger. Chat without distractions on any OS.
ooVoo offers an easy way to have a face-to-face video chat with friends, family or colleagues.
A playcast is a podcast that you create out of a playlist. Using Playcaster and built in features of OS X, you can share your playlists with friends. Playcaster combines all of the songs from an iTunes playlist into one large mp3, then uses OS X web sharing to build a podcast out of your playcasted playlists. Your friends can subscribe to your feed in any RSS reader or iTunes and listen to your playlists.
Smiley is a small application that makes it easy to add new emoticons to iChat and iChat AV applications. With Smiley, you can add prebuilt emoticon packs or create your own images and add them easily and quickly.
The Manor is a 2D visual chat experience with Python development tools.
(commercial) a handy small solution, which downloads several files using a single link/URL at once