Here's the scoop on who make what for whom. Remember that a manufacturer will always try to ensure that their brand has tightest quality control.
NEC - Nec is a OEM manufacturer, The company's plan is to supply industrial unit under the NEC name and supply home units thru rebadges such as Marantz and RCA, Sony and Runco.
Panasonic - Makes the complete units, Supplies Toshiba, JVC, Fujitsu and more
Pioneer Plasma - Makes all of there own equipment and sells OEM to Sharp and Sony Note: The 5040 and 4340 HD multimedia box is made by Sharp Note : Pioneer Electronics now owns NEC and the Pioneer 424 EDTV unit is basically a NEC 42 rebadged
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, 42inch EDTV is NEC. 50 inch is a Pioneer 504 based unit
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 appears to be their own
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
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 .
Runco - OEM 50" from Pioneer and 42" from NEC,
Marantz - OEM 42" plasma monitor from NEC.
Studio Experience use a Samsung panel but custom electronics
Viewsonic - OEM 50" plasma screen from Pioneer ( old 502 ). 55 is Hitachi
Sampo - 42v3 is old Fujitsu, 42v6 is Samsung Plasma,
Gateway: Units are rebranded Sampo
Norcent Units may be rebranded Sampo
Maxcent is a rebranded Sampo
Prima, SVA, Akai, and the hundreds of other no name plasma screens are all chinese made.