Acapella
ACC Microelectronics
Acer Labs
Actel
Adaptec
Advanced Hardware Architectures
Advanced Linear Devices
Advanced Power
AKM Semiconductor
Alcatel Microelectronics
Allegro Microsystems
Alliance Semiconductor
Alpha Industries
Alpha Semiconductor
Altera
AMCC
AMD
AMI
Anadigics
Analog Devices (+PMI)
Apex
ARM
Array Microsystems
ATecoM
Atmel
AuraVision
Avance Logic

Benchmarq
Brightflash
Brooktree
Burr-Brown
Butterfly DSP

C-Cube
Catalyst Semiconductor
Cherry Semiconductor
Chips and Technologies
Chrontel
Cincinnati Electronics
Cirrus Logic
CP Clare
CML
CommQuest
Cree
Crosslink Semiconductor
Crystal Semiconductor
Cypress Semiconductor
Cyrix

Dallas Semiconductor
Data Delay Devices
Delco Electronics
Dialog Semiconductor
Digital Semiconductor

ESS Technology
Echelon
Elantec
Enhanced Memory Systems
Epson (point of sale, see also Seiko Epson)
Ericsson
EXAR (+Startech+Micro Power Systems)

Fairchild
Fujitsu Microelectronics, Compound Semi

Galileo
General Semiconductor
Genesis Microchip
Gennum
GHz Technology (+CTC+Acrian)
Graychip

Harris
Hewlett-Packard
Hitachi
Honeywell
Hyundai Electronics America

IBM Microelectronics
ICS
ICT
IDS Electronics
ISD
ISSI
ITT Semiconductor
ITT-GTC (GaasTek)
I-Cube
Integrated Device Technology (IDT)
Intel
International Rectifier
IMP
IXYS
8x8 (IIT)

Lambda Advanced Analog
Lansdale
Lattice
Level One
Linear Technology, (search)
Linfinity Microelectronics
LOGIC Devices
Lucent Technologies (AT&T Microelectronics)
LSI Logic

MMC Networks
M/A-Com
MX-COM
Maxim
Macronix
Micrel
Microchip Technology
MicroLinear
Micron
Microsemi
MicroUnity
Micro Networks
MIPS Technologies
Mini-Circuits
Mitel
Mitsubishi Semiconductor
Mosel Vitelic
Motorola Semiconductor
Music Semiconductors
Myson Semiconductor

National Semiconductor
NEC Components
Newport Components
Nichia
NJR (New JRC)
Novalog
NTE

OKI
OPTi
Orbit

Panasonic (Matsushita)
Paradigm
Performance Semiconductor
Pericom Semiconductor
Philips Semiconductor (Signetics)
Phylon
Pico
Plessey Semiconductors
PLX Technology
PMC-Sierra
Power Convertibles
Power Integrations
Power Trends
PowerTech
Pulse Engineering

QT Optoelectronics
QED, Inc
Quality Semiconductor
QuickLogic
QLogic

Rambus
Ramtron
Raytheon Semiconductor
Rendition
RF Microdevices
Rockwell
ROHM

S3
S-MOS
Samsung
SanDisk
Sanyo
SaRonix
SEEQ
Seiko Electronic Components Division
Seiko Epson
Semicoa
SGS-Thomson (+Inmos)
Sharp
Siemens
Signal Processing Technologies (SPT)
Silicon Engineering
Silicon Microstructures (EXAR)
Silicon Systems
Simtek
Sipex
SMC
Sony
Stanford Telecom
Sun Microelectronics
Supertex
Symbios Logic (NCR Microelectronics)
Synergy Semiconductor

Taiyo Yuden
Teccor
TelCom
Teltone
Temic (Telefunken+Siliconix+MatraMHS)
Texas Instruments
Thaler
Tundra
3Dfx
3Dlabs
Toko Semiconductor
Toshiba usa, jp
TransSwitch
TriTech Microelectronics
TriQuint

Unitrode
USAR
U.S. Digital
UTMC

Vantis
V3
VIA
Valor Electronics
Vitesse Semiconductor
Vivid
Wafer Scale Integration
Winbond
Westcode Semiconductor

Xecom
Xilinx
Xicor

Yamaha

Z-Communications
Zetex
Zilog
ZMD

Other resources :
Jaap van Ganswijk's Chip Directory

InfoQuick (Very well executed data sheet repository)
TDS-NET (Data sheet archive with search engine)
AT&T Toll Free Directory (Electronic Components Section)
AT&T Toll Free Directory (Semiconductor Devices Section)
Distributors Index
EEM
IC Master
PartNET
Thomas Register
FAST Electronic Broker
QuestLink (Data sheet archive with search engine)