ITPRC - Data Link

ATM

ATM Forum - Just about anything you want to know about ATM can be found here
ATM News Digest - A daily journal for broadband networking
ATM Report - International newsletter devoted to ATM
ATM Tutorial - Very thorough tutorial of ATM, from RAD Networks
Cell Relay Retreat - Archives to the cell-relay mailing list, several other ATM-related mailing lists, and many other resources
Designing ATM Internetworks - By Cisco Systems Inc. Comprehensive guide to ATM and ATM design issues
comp.dcom.cell-relay FAQ - ATM Frequently Asked Questions

Ethernet

Charles Spurgeon's Ethernet Home Page - Perhaps the best collection of Ethernet resources on the web
Configuring Spanning Tree PortFast, UplinkFast, and BackboneFast - Cisco's configuration guide to the various flavors of STP
Ethernet FAQ - FAQ for the comp.dcom.lans.ethernet newsgroup
Ethernet Type Codes Master Page - A listing of Ethernet code types
Gigabit Ethernet - Information on Gigabit Ethernet including history and standards
Gigabit Ethernet Links Page - IEEE's links to Gigabit Ethernet Information
IEEE 802.1 Home Page - Index of various IEEE 802.1 working groups
IEEE 802.3 Higher Speed Study Group - Home site for developers of the 10 Gigabit Ethernet standard
Jumbo Frames - Information and papers on Jumbo Frames
OUI and Company_id Assignments - IEEE's OUI and Assignment database
10 Gigabit Ethernet Alliance - Industry forum for advancing 10 Gigabit technologies

Frame Relay

Basic Guide to Frame Relay Networking - The Frame Relay Forum's guide to understanding Frame Relay
Configuring and troubleshooting Frame Relay - Cisco's guide to configuring and troubleshooting frame relay using Cisco routers
Frame Relay - Cisco's guide to Frame Relay standards and applications
Frame Relay Resource Center - Comprehensive collection of Frame Relay tutorials and resources
Frame Relay Resources - From Motorola Inc.
The Frame Relay Forum - Association for the implementation of Frame Relay. Lots of good frame relay information

ISDN

ISDN Tutorial - Detailed tutorial on ISDN technologies and applications. By Ralph Becker

Miscellaneous

Data-Link Switching - Cisco's guide to DLSW
High Speed Networking Pages - Tons of links to high speed networking technologies.
LAN Switching - Cisco's overview and configuration guide for LAN switching
Ryan's Gigabit Network & Distributed Computing Home Page - Collection of links to research projects on gigabit networking

Token Ring/FDDI:

FDDI Fundamentals - A short overview of FDDI
FDDI - System Level Description - A detailed white paper on FDDI technology
Token Ring FAQ - FAQ for the comp.dcom.lans.token-ring newsgroup. One of the few sources left on the web for Token Ring information
Token Ring / IEEE 802.5 - Cisco's technology guide for Token Ring

VLANs:

LAN Switching - Cisco's guide to Layer 2 switching and VLANs
The VLAN Report - a comprehensive guide to VLAN technologies and applications, from 3Com