Actually, there are 4, bro. And the great SONY ISNT ONE OF THEM !

...sorry SONY fans !
2 from Japan
Pioneer
Panasonic
2 from Korea
LG
Samsung
bro htkaki is absolutely right..most people simply buy cos their neighbour got la, their friend got la, status la...but they havent got a clue on what to buy, what they need, what they should, what they shouldnt etc...all they know is from listening to salesman or friends etc. or bcos the design is nice la, advert is cool la, shape is nice la etc. Flat TV is the CRAZE now, and manufacturers know that. They also know that there are those who is willing to get the latest n best tech at whatever price. I pity these misguided buyers who are influenced by salesman into buying the latest techs saying its the best etc but later find out they dont need it in the first place.
Something I found....
THE MAJOR PLASMA TELEVISION MANUFACTURERS
NEC - Nec is a OEM manufacturer and is now owned by Pioneer. Although owned by Pioneer they still operate under a separate label. NEC has commercial units and home units. They also supply screens to Marantz Runco and several other companies. NEC sold their plasma factory to Pioneer and now buys their panels from Pioneer and installs their own electronics.
Panasonic - Makes the complete units, Supplies Toshiba, JVC, Fujitsu and more
Pioneer Plasma - Pioneer owns NEC and has switched production to the NEC lines. The new 50 inch and the 42 inch units are all NEC glass. To tell if a 50 inch is Pioneer or NEC, check the resolution, If 1280 it is Pioneer , If 1365 it is NEC . 42 inch Pioneer Plasma TV is NEC . 43 inch Plasma TV is Pioneer Glass
Fujitsu Plasma - Only makes their own 42 inch in partnership with Hitachi . 50 and 61 inch Fujitsu Plasmas are Panasonic and NEC but the 42 inch are their own. Note Hitachi plasma screens are identical to Fujitsu and cost thousands less, 55 Inch Fujitsu is same as Hitachi,
Sony Plasma TV - Makes their own boards and chips but uses Fujitsu/ Hitachi plasma screen glass for 42 inch, 50 inch is NEC, 42inch EDTV is NEC
Hitachi - Owns 50% of plasma screen factory with Fujitsu. Makes own internal components. 42 Alis screens are Hitachi as is the New 55, 50 inch are Pioneer and 42 EDTV is a NEC screen
Philips - Uses Fujitsu/ Hitachi glass screen and most internal components as well. However, Philips makes its own bezel with built in speakers.
LG / Zenith - Make their own glass in Korea
Samsung - Makes its own components in Korea
THE SECONDARY MANUFACTURERS
RCA/ Thompson - Partners with NEC to OEM its product. Just a NEC with a new bezel.
JVC - 50 inch is Panasonic, 42 is NEC
Toshiba - OEM from Panasonic.
Sharp - OEM product through Pioneer for 50" and 42 though they may make some internal component changes.