thingk.me

Clayster's thingk.me provisioning server uses a set of open, in the public domain, interoperable APIs to help devices in the Internet of Things make security decisions. With the API devices delegate security decisions to thingk.me and follow its recommendations. Using the XMPP protocol, the API also allows devices in the Internet of Things to create accounts, register devices, and make decisions about which other devices to trust, what they can do and who can do it. The API also supports interoperability between devices.

XMS

XMS is a smartphone app that provides free, real-time, unlimited messaging over the user's internet connection. Users can send messages containing text, images, videos, locations, emoticons, and other content. XMS supports both individual and group messaging. Developers can integrate XMS into their applications by using XMPP (formerly known as Jabber).
XMS

HIV Drug Research Center

The HIV Drug Research Center provides a pair of APIs for predicting the susceptibility of mutated HIV to a variety of drugs. One API predicts the susceptibility of mutations in HIV protease to amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinanvir. The other predicts the susceptibility of mutations in HIV reverse transcriptase to lamivudine, abacavir, zidovudine, stavudine, zalcitabine, didanosine, emtricitabine, and tenofovir. These APIs are available to users via REST and XMPP.
HIV Drug Research Center

Google Cloud Print

Google Cloud Print is a service that enables any app (web, desktop, or mobile) on any device to print to any printer anywhere in the world. The APIs allow the apps to collect the necessary data to show their own user interface for custom print options or use the common print dialog that Google Cloud Print provides. There are also APIs for querying print job status. The API uses XMPP protocol and responses are formatted in XML, JSON and TXT. Google Cloud Print is not currently available.
Google Cloud Print

Telenor SMS

Telenor is a mobile carrier based on Norway. The Telenor SMS API provides access to the company's text messaging service for business-to-business and business-to-consumer bulk messaging needs. The company provides short and whole numbers for sending and receiving text and MMS messages. There are various options for using the API, including SOAP and XMPP protocols. No public documentation is available. Coverage: norway (messages can be sent to foreign subscribers, but available countries not listed)
Telenor SMS

Facebook Chat

This API allows users to integrate Facebook Chat into their Web-based, desktop, or mobile instant messaging products. The user's instant messaging client connects to Facebook Chat via the Jabber/XMPP service. Responses are formatted as XML or vCard.
Facebook Chat

Notifixio.us

The Notification Platform API allows you to create channels through which users can be notified (either XMPP or HTTP based), create sources that users can choose to follow, create subscriptions, and more. The Notifixio.us main site is for being notified on channels you already use when new items are added to a website you specify.
Notifixio.us

identi.ca

Use the identi.ca API to include Identi.ca either as an option in your programs or as the main platform for development. The Identi.ca API supports an API compatible with Twitter's, based on the open source project StatusNet. Identi.ca users can post small (140 chars or less) text notices and also subscribe to others' posts. Also, Identi.ca now supports a full feed of the public timeline via XMPP, which is likely most useful for data aggregators. Identi.ca is different from Twitter, Jaiku, Pownce, Plurk, and others because it is open, transparent, built on free software, and all the data is openly available via the Creative Commons Attribution license.
identi.ca

Google Talk

From the site: As long as you adhere to the requirements of the XMPP specs, you should be able to connect to the Google Talk service. Other clients that can connect include [[http://gaim.sourceforge.net/ GAIM]] and [[http://www.ceruleanstudios.com/learn/ Trillian Pro]].
Google Talk