Photo credit: Baloncici

1. ShowMyPC: Free desktop sharing and remote control software for Windows
2. Goowy: Web-based desktop allows you to chat on multiple IM networks, share files, and organize your contacts
3. Talkster: Provide two phone numbers, and get a local area number to connect them
4. Adium: Free Mac OS X instant messaging application enables you to connect to all major IM services

1. ShowMyPC
   
   ShowMyPC is a free desktop sharing and remote control software. The two users just need to download the software and can access each other's PC with just a password (no IP address needed)which is automatically generated when you start the viewing session and must be provided to the remote user by email, phone or other means. No registration is required, just a 900kb download. Free to use.
   http://www.showmypc.com/





2. Goowy
   
   Goowy is a web-based desktop that anyone can use to collaborate with his team members anywhere, anytime. In fact it features: a multi-protocol instant messaging system that allows you to access MSN, Yahoo!, Gtalk, and obviously Goowy network, a file sharing system that gives 1GB of storage space, contacts, and calendar. All you need to do before start using Goowy is to fill in a simple registration form. Free.
   http://www.goowy.com/





3. Talkster
   
   Talkster, which previously was a mobile instant messaging system, has now become a way to have free calls with anyone. By providing your and your friend's number, you two will be automatically given a local area number to call to get your two phones connected, so that if you have a data plan for your region you will be talking for free, or at least at very low rates. No registration is needed, and it is free to use.
   http://www.talkster.com/





4. Adium
   
   Adium is a free instant messaging application for Mac OS X that enables you to connect to AIM, MSN, Jabber, Yahoo, Gtalk, and more networks at once. You can organize your contacts in a customizable contact list, have multiple and tabbed conversations, support for multiple statuses on the different networks, emoticons, and message history. Completely free to download and use.
   http://www.adiumx.com/