Campfire is a business-oriented online chat service.
SpecsUpdate
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Pros
Pro Supports optional 128-bit SSL encryption
Pro Guest access
You can invite people to join conversations even if they don't have a Campfire account. Campfire will generate a link to share and the guest will only need to enter their name to join the conversation.
Pro Easy conferencing
When you need to make a conference call, all you need to click is "Start A New Call" and Campfire instantly embeds a phone number and password code in the message thread.
Pro Mobile apps
Campfire supports only iOS, but third party apps can be used for Android. There are also other third party apps that build upon Campfire and extend its functionality.
Pro Embeds images
Images that are uploaded in the GIF, PNG, or JPEG formats are represented as thumbnails in the chat room.
Cons
Con Future of Campfire is uncertain
37signals have "changed direction" away from Campfire, focusing on Basecamp. They've ruled out shutting it down, but at this stage it's uncertain whether it'll be spun off as a separate company, sold off, or run in maintenance mode without any new features.