Intel MCS 51-251 Microcontrollers
Intel's 8-bit MCS® 51 family of microcontrollers development site. Technical documents, support, FAQ.
http://developer.intel.com/design/mcs51/cf_51.htm

ST Anglia Microcontroller Design Group
Distributor of ST microcontrollers including diodes, regulators, thyristors, transistors, ICs, microcontrollers, memory and heatsinks. Online line card, data sheets, application notes and tools.
http://www.st-angliamicro.com/

Microchip Technology Inc
Microchip Technology Inc. is a Leading Provider of Microcontroller and Analog Semiconductors, providing low-risk product development, lower total system cost and faster time to market for thousands of diverse customer applications worldwide.
http://www.microchip.com/

ZiLOG
Application notes on the Z8 series Microcontrollers.
http://www.zilog.com/products/appnotes.asp

Asl
Free, powerful cross assembler for many microcontrollers and processors.
http://john.ccac.rwth-aachen.de:8000/as/

PicForth
Unix or Linux hosted Forth compiler for PIC 16F87x and 16F88 microcontrollers
http://www.rfc1149.net/devel/picforth.html.en

Silicon Storage Technology, Inc. (SST)
Manufactures flash memory and microcontrollers.
http://www.sst.com/

Atmel Wireless and Microcontrollers
ICs for innovative solutions in RF, automotive and communications.
http://www.atmel-wm.com/

WebRing: AVR
AVR mcu related sites
http://www.webring.com/hub?ring=avr

WebRing: PICmicro
A collection of websites about the Microchip PIC microcontroller and related projects.
http://www.webring.com/hub?ring=picmicro