You can download Microsoft Office Communicator Mobile.
Overview:
Communicator Mobile extends the reach of Live Communications Server 2005 to information workers who use Windows Mobile based devices. Communicator Mobile offers a similar look and feel to the desktop version of Microsoft Office Communicator 2005, and it ensures that access to capabilities that are provided by Live Communications Server 2005 continues when users are away from their desks.Communicator Mobile is available in four editions for Windows Mobile based devices, depending on which operating system the device is running. The installation file for each operating system is as follows:Windows Mobile 2003 SE for Pocket PCsDownloadable file name: CommunicatorMobile_PPC2003.msi. Windows Mobile 5.0 for Pocket PCsDownloadable file name: CommunicatorMobile_PPC50.msi. Windows Mobile 2003 SE for SmartphoneDownloadable file name: CommunicatorMobile_SP2003.msi. Windows Mobile 5.0 for SmartphoneDownloadable file name: CommunicatorMobile_SP50.msi.