The carriers announcing their support for Mozilla Firefox OS, a new mobile Linux-based operating system built around Firefox and web technologies, include: América Móvil, China Unicom, Deutsche Telekom, Etisalat, Hutchison Three Group, KDDI, KT, MegaFon, Qtel, SingTel, Smart, Sprint, Telecom Italia Group, Telefónica, Telenor, TMN, and VimpelCom.
In terms of hardware coverage, "We are working with manufacturers Alcatel (TCL), Huawei, LG and ZTE to build the first Firefox OS devices, all powered by the Qualcomm Snapdragon chipset." Last month they announced Firefox OS preview phones that were rather unimpressive.
Mozilla expects to begin shipping actual Firefox OS phones later in the year.
More details on the latest Firefox OS happenings can be found from this Mozilla.org blog post.