If you are looking for some useful engineering software, or instructions on how to use it, or understanding an engineering principle better, or a data sheet, you might find what you are looking for here.
Data Sheets:
TTL Data Sheets Most of the popular ones are here.
TTL Data Sheets Complete line of FAST, CMOS, Low-Power Schottky, etc. from Phillips.
Transistors, Diodes, and Voltage Regulators: Data sheets for some common ones are here.
Tutorials:
Xilinx ISE 8.2i Quick Start Tutorial by Xilinx. This "Official" tutorial for ISE version 8.2i is published by Xilinx.
Xilinx ISE 6.202i Tutorial by Michael Ciletti. This is for an older version of ISE than the one currently in use, but most of it is still useful.
Verilog Tutorial: Very good tutorial, with code examples.
Interactive Verilog & VHDL Tutorials: Download the one you want. Aldec requires that you register or a free license, but it is worth the effort.
The Verilog HDL: Tutorial on PDF slides from Carnegie Mellon University.
Handbook on Verilog HDL: Tutorial at Bucknell University.
The Designer's Guide to Verilog: Background information and brief tutorial for Verilog.
The Designer's Guide to VHDL: Background information and brief tutorial for VHDL.
Digital System Tutorial (Part 1): Digital concepts, number systems & codes, logic gates, Boolean algebra.
Digital Systems Tutorial (Part 2): Flip flops, counters, registers. (Just turn off your speakers!)
Digital Systems Tutorial (Part 3): Synchronous & asynchronous operation, state tables, state diagrams, analysis & design of sequential circuits, design of counters.
All About Circuits - Digital: Boolean Algebra, logic gates, combinational logic, principles of computing (sequential logic).
All About Circuits - Semiconductors: Online "book" covering many of the topics we discuss in this course.
Principles of Semiconductors: Online "book" by Bart Van Zeghbroeck.
Software:
On-Line Logic Simulator: Design and simulate digital circuits on-line.
K-Map Software: Works for up to 8 variables.
FREE Digital Works Software: This is a Freeware program that allows hierarchal digital circuit design and simulation. Also download a basic tutorial, Getting Started with Digital Works, by Dan Stanzione.
FREE CircuitMaker Software: This is a student version of CircuitMaker 6. You may download and use this free circuit design/simulation software on your personal computer. It allows you to enter your analog or digital circuit as a schematic and then simulate its operation.
FREE PAL Programming Software: This DOS-based compiler may be run directly from a floppy disk. No hard disk installation is necessary. It also contains examples of how to program a G16V8 as a combinational logic circuit, as a synchronous counter, and as a state machine.
DEMO CUPL Software: This "Starter Kit" is a compiler that produces JEDEC files for programming PALs and GALs. It is a demo version of WinCUPL that is good for 30 compiles. Also download a basic tutorial, CUPL Tutorial. This is not a complete instructional manual as it only contains the items necessary to create most general types of programs.
FREE WinCUPL: Compiler for Programmable Logic Devices (Free student version). This is an earlier version of the WinCUPL described above, but it does not expire after 30 compiles. The serial number you should enter is 66999998. A User's Guide is also available.
FREE PSpice Software: This is an evaluation version of a popular circuit simulation package. It is powerful enough for most school projects. The schematic capture module may even be used to create schematic diagrams for your formal lab reports. This program is too long to download, so you will be sent a CD instead.
FREE Xilinx ISE WebPACK: Software to implement Verilog (or VHDL) designs on Xilinx FPGAs.
FREE Orcad VHDL Power Pack: Here is an HDL evaluation package. Login as "guest".