Open Handset Alliance is a group of 47 technology and mobile companies who have come together to accelerate innovation in mobile and offer consumers a richer, less expensive, and better mobile experience. Together they have developed Android, the first complete, open, and free mobile platform.

Open Handset Alliance unveiled Android, an open source mobile phone platform based on the Linux operating system. An early look at the SDK was released to developers on 12 November 2007. The first commercially available phone running Android is the the HTC Dream.

Open Handset Alliance was stablished on 5 November 2007 by Google Inc. and as of now following companies are the members of this group:

Software Companies
Ascender Corp.
eBay Inc.
Google Inc.
LivingImage LTD.
Myriad
Nuance Communications, Inc.
OMRON SOFTWARE Co, Ltd.
PacketVideo (PV)
SkyPop
SONiVOX
SVOX
Commercialization Companies
Aplix Corporation
Borqs
Noser Engineering Inc.
TAT - The Astonishing Tribe AB
Teleca AB
Wind River
Semiconductor Companies
AKM Semiconductor Inc
Audience
ARM
Atheros Communications
Broadcom Corporation
Intel Corporation
Marvell Semiconductor, Inc.
NVIDIA Corporation
Qualcomm Inc.
SiRF Technology Holdings, Inc.
ST-Ericsson
Synaptics, Inc.
Texas Instruments Incorporated
Handset Manufacturers
Acer Inc.
ASUSTeK Computer Inc.
Garmin International, Inc.
HTC Corporation
Huawei Technologies
LG Electronics, Inc.
Motorola, Inc.
Samsung Electronics
Sony Ericsson
Toshiba Corporation
Mobile Operators
China Mobile Communications Corporation
China United Network Communications 
KDDI CORPORATION
NTT DoCoMo, Inc.
SOFTBANK MOBILE Corp.
Sprint Nextel
T-Mobile
Telecom Italia
Telefónica
Vodafone

For more information visit official site of Open Handset Alliance