Scopserv Communicator is an audio/video Internet phone and instant messenger that supports some of the most popular VoIP and instant messaging protocols such as SIP, Jabber (XMPP), AIM/ICQ, MSN, Yahoo! Messenger, and a whole lot of other useful features. ScopServ Communicator is based on the SIP Communicator softphone.
nimsg (the Network Instant MeSsenGer) is a compact, server-based chat program. Its features include the ability to chat with more than one person at the same time, the ability to post multiple times in a row, and the ability to let users choose their in-chat nicknames. It can be used as an alternative for IRC, for those times where you just want to have a small, local chat room.
SaluSafe is an encrypted email, chat, and file storage and sharing system. Your email and files are highly encrypted end-to-end, and cannot be intercepted by any third party. It was built from the ground up for security via strong cryptography, and is not just another security wrapper on top of an existing email solution.
Messenger++ is a multi-protocol instant messaging client for Android. It features multi-protocol support (currently: XMPP, Facebook(XMPP), Google Talk(XMPP), VK, SMS) + audio calls if supported by the protocol. The UI is optimized for tablets. It is a Maven-based project with Robolectric tests built by Travis CI.
SecuXabber is a secure Jabber-client for Android that uses strong, asymmetric encryption on top of the XMPP protocol. A key pair is generated on application start-up. Users can send their public key to other SecuXabber users via Bluetooth. This face-to-face check ensures the veracity of the public key. After the keys have been imported by both users, all communication between them is encrypted using strong 4096 bit encryption. It supports all relevant XMPP features, works with multiple accounts, is highly customizable, and has many other useful features.