Photo credit: Fotoflash

1. AllPeers: Firefox extension allows you to chat and share files
2. File.io: Create an online folder, upload files, and share them
3. Universal Messenger Plus: Connect to major instant messaging service with a simple interface
4. Social.im: Chat with all of your Facebook contacts directly

1. AllPeers
   
   AllPeers is a Firefox extension, and therefore compatible with Windows, Mac, and Linux, that allows you to chat, share files and web pages, and also to download torrent files. After a free registration, you can add all of your friends, chat with them, and send them files and web pages by drag&dropping them on their name. Free to download and use.
   http://www.allpeers.com/





2. File.io
   
   File.io is a free online service that anyone can use to create an online folder (or more) where you can upload and share your files. After you give your folder a name and a password, with no registration process, you can start upload your files in your 150MB online folder. You will then need to share with your team the name and the password for that folder so that they can access and download them. Free to use, no registration needed.
   http://file.io/





3. Universal Messenger Plus
   
   Universal Messenger Plus is a free instant messaging software that anyone can use to connect to ICQ, MSN, AOL, IRC, Yahoo Messenger, and Jabber networks simultaneously. The interface its really simple featuring just a single contacts list, with the possibility of creating contact groups, and that places an icon next to every contact to immediately recognize on which network that contact is. UMP is free to download and use.
   http://www.universalmessengerplus.com/





4. Social.im
   
   Social.im is a new instant messaging service that allows you to connect with all of your Facebook contacts. It doesn't matter if they have Windows Live Messenger, Yahoo Messenger, Skype, Gtalk...You can all have text-chats on social.im just using your Facebook's accounts. It offers a really clear buddy list, and completely integrates with Facebook's events. Free to download and use.
   http://www.social.im/