We have a local XMPP server set up on the network, and we all use various different clients, I personally use Adium, we have some developers using Empathy on Linux, and others using Pidgin on Windows.
Jenkins has an account on said XMPP server (our AD logins actually) and is thus able to send messages to the developers that are signed on. We also have a "conference room" set up on XMPP that every developer is logged in to most of the time, and Jenkins is available there to run commands, so you can for instance say !build android-client and it will start building the android client, test it in the emulator and report results to the chat room.
I don't know what XMPP server we are using. I was not the one that set that up. I only have access to all of the FreeBSD/Linux machines in the company, someone else gets the pleasure (or should I say displeasure) of managing all of the Windows server infrastructure (AD, File servers, stuff like that), including where our XMPP service is being run because it requires AD access. Upsides and downsides to being the only developer in the company that knows Unix...
We have a gitorious server that also has a jenkins account (jenkins connects over SSH). It is running within a VMWare Virtual Machine with access to 4 cores running at 2.4 Ghz, and 14 GB's of ram. Whenever jenkins notices a change in git (using polling, every 5 minutes, set up for now, eventually I'll get around to doing push notifications of some sort ...) it pulls down the latest source code, and starts up the Google Android emulator (basically qemu for the ARM platform with the devices as an Android phone would have them), once that is started up it compiles the source code (java) and using adb installs it on the phone, runs the test suite, and reports any errors back, Jenkins then shuts down the emulator.
It isn't extremely fast, starting up the emulator takes about 50 seconds or so, and I am trying to get a faster server to use as a jenkins build slave, but for now it works wonderfully. Everything I mentioned is completely managed by jenkins.
Jenkins has an account on said XMPP server (our AD logins actually) and is thus able to send messages to the developers that are signed on. We also have a "conference room" set up on XMPP that every developer is logged in to most of the time, and Jenkins is available there to run commands, so you can for instance say !build android-client and it will start building the android client, test it in the emulator and report results to the chat room.