There is chat in spreadsheets and, thought it is sometimes hard to negotiate, there is chat in the text editor, too.
Released ~ 2008. Chat is a persistent gadget on the homepage; you can hide it by changing the settings. Gadget is supposed to display Google Video, YouTube, Picasa Web Album, and Flickr URLs directly in the chat window but I haven’t been able to get this to work.
Not all clients support file transfer: iChat, for example. Saves the file in a folder named Google Talk.
Downloaded and installed on your computer. Released in 2005. Client only for Windows but video chat available for both pcs and macs. Voicemail can be up to 10 minutes long.