The following links will take you to various tutorials and references on key subjects in mechatronics. If you come across some other high quality tutorials or references that are not listed here, please e-mail me the URL.

Electronics

(general)

• All About Circuits A fantastic site covering electricity and electronics
• Fundamentals of Electrical Engineering and Electronics Extensive e-book with great explanations
• The Electronics Club Well illustrated, also has a guide to soldering
• DC Electronics A nifty tutorial on basic electronics; includes self-tests
• The Electronics Tutorial A nice overview of basic electronics
• Electricity and Magnetism Comprehensive coverage of electricity and magnetism concepts
• Basic Electronics Guide A clear but brief coverage of many concepts in electronics
• Electronics Tutorials Glen Willamson's eclectic but very interesting site
• MIT Open Courseware MIT OpenCourseWare in Electrical Engineering and Computer Science
• Online Books on Electronics From AVRfreaks community forum
• Op-amp Electronics Tutorials Basic fundamentals of electricity and electronics by Tony Kuphaldt

Digital Electronics

(See the general electronics links also)

• All About Circuits Chap 4 A nicely done tutorial on digital electronics
• Logic Simulator Drag-and-drop logic gates and see how combinational logic circuits function
• ADC/DAC Operation Nice overview of how analog-to-digital and digital-to-analog converters work

Components

(See the general electronics links also)

• Resistor Color Code Resistor color code from Leon Audio
• Standard Resistor Values Standard EIA decade resistor value table
• How to Read Capacitor Codes How to read a capacitor code
• Diodes Good overview of diodes
• Light Emitting Diodes (LEDs) Good overview of LEDs
• Inductors Good overview of inductors
• Transistors Good overview of transistors
• The Transistor Story The history of how the transistor came to be, plus TONS more information!
• MOSFETs Good overview of MOSFETs
• Power MOSFET Basics More in-depth overview of how Power MOSFETs are constructed and function
• Op-amp Basics Nice overview of operation amplifiers from National Semiconductor
• Op-amp Applications Book Analog Device's extensive coverage of op-amps and their applications
• The Monolithic Op-amp Robert Widlar's classic app note on op-amps
• Op-amp Applications Guide Walt Jung's comprehensive guide to op-amps
• Op-amp Circuit Collection Extensive collection of applications of op-amps
• Op-amps for Everyone Texas Instrument's extensive design reference on op-amps
• 555 Timer Tutorial Fantastic tutorial on the highly versatile and useful 555 timer
• Battery University Extensive coverage of batteries

Motors

• Electric Motors and Generators An introduction using animations and schematics to explain the physical principles of motors, generators and transformers
• DC Motor Tutorials Lots of good information about dc and stepper motors from MicroMo Electronics
• DC Motor Principles Fundamentals of ironless armature dc motors From Portescap
• Control of Stepping Motors Doug Jones' excellent tutorial on stepper motors
• Salvaging stepper motors from e-waste 
• Motor Overview Has a good overview of dc motors and lots of interesting links at the end
• Motor Fundamentals Links Links to app notes on motors from Microchip

Programming

• Essential C A good brief overview of C
• C Tutorial for Beginners A comprehensive tutorial for C from fresh2refresh.com
• Common C Programming Errors Helpful list of common errors
• Programming with lcc-win32 A good tutorial on C. See also https://lcc-win32.services.net/ for a C compiler that is free for non-commercial use
• C programming course Univ. of Strathclyde's course on C programming
• C Programming Tutorial An entire site for learning C and C++ programming
• Programming in C Resources Another good list of C programming resources
• Online Books on C from AVRfreaks Nice collection of links contributed by AVRfreaks
• Programming in C Covers ANSI C, history, culture, and other sources about C
• Developing Embedded Software in C Jonathan Valvano's extensive work on embedded systems
• Programming Embedded Systems Michael Pont's excellent books
• AVR Studio Tutorial by Derek Molloy YouTube video 
• AVR Interrupt Tutorial YouTube video by Saravanan AL 
• MATLAB Tutorial MathWorks excellent tutorials on all things MATLAB
• Java Tutorial Comprehensive Java tutorial
• SQL Tutorial Comprehensive SQL tutorial. See also this list of SQL tutorials.

Microcontrollers, et. al.

• Choosing a microcontroller Gives a nice overview of what a microcontroller is
• The PIC Microcontroller Book Focuses on PIC microcontrollers, but the Introduction gives a good overview of what a microcontroller is
• Microcontroller FAQ A little dated, but has good information
• Programmable Logic Controllers The place for PLC's!

Prototyping

• Soldering Video EXCELLENT, 7 minute video showing how to solder!
• The Basic Soldering Guide Great overview of how to solder. Don't miss the photo galleries that accompany this site.
• How to solder Metal blog post with ots of links to other helpful resources related to soldering (thanks to Sophie for this link!)
• How to Solder SMT Devices Good resource on how to solder the more modern surface mount components
• Low-Cost SMT Soldering Guide Nice guide for soldering surface mount components
• Learn How To Solder: Repairing Electronics & Appliances A nice collection of links related to soldering for many different situations
• How to Wire-Wrap Good overview of a helpful prototyping skill
• How to Develop and Prototype a New Product Read this before you do any prototyping! Very helpful tips.
• Prototyping Techniques and Soldering Good introduction to schematics, assembly methods, and soldering
• Manhattan/Dead Bug/Ugly circuit construction techniques These techniques can result in very high performance prototypes (see this video for a way to make the 'islands' using a spot weld cutter: https://www.youtube.com/watch?v=0QbeC0Hw2QA
• High Speed Op-Amp Circuit Tips techniques for working with high frequency op-amps
• Circuit Maker Simulation Software Freeware (limited) version of a good circuit design and simulation software
• Embedded Systems Development Jack Ganssle's archive of articles on embedded systems development

Interfacing

• Beyond Logic Lots of information on interfacing
• Controlling the Real World With Computers Lots of practical information on interfacing computers to hardware
• Interfacing the standard parallel port Nice coverage of the standard parallel port and how to interface it
• Parallel port interfacing made easy Tomi Engdahl's extensive guide to the parallel port. Very nicely done.
• Interfacing the PS/2 Mouse/Keyboard Good coverage on interfacing PS/2 mouse or keyboard
• Keyboard Scancodes Extensive treatment of data sent by various keyboards and PS/2 mouse

Sensors

• How PIR motion detectors work Good overview of how an infrared motion detector works.
• Wireless and Amateur Radio
• Antennas 101 Introductory guide to antennas and how they work
• Antennas 102 More Q&A A few more questions and answers following the previous article
• J-pole antenna Simple instructions to create a portable, flexible antenna for 2m and 70cm operation
• Amateur Radio Homebrew Antennas and Antenna Theory Huge collection of links to antennas for all bands and antenna theory

Others

• Relay Coil Transient Suppression Comparison of methods and recommendations for suppressing inductive transients in dc relays
• Coil Suppression and Relay Life How suppression methods affect relay contact life
• XY Plotter A nice example of a complete mechatronics project
• PIC microcontroller programming tutorial and Instructables resource for programming the PIC microcontroller
• ePanorama A wealth of resources and links on electronics
• Custom Characters on a Character LCD Display How to display custom bit-mapped graphics on a character LCD. Has a link to HD44780 information.
• instructables.com Step-by-step instructions on how to make lots of interesting things
• Learning Linux Well organized overview of how to use Linux
• Tex Tutorial 1 Nice online tutorials on Tex
• Tex Tutorial 2 The Not So Short Introduction to LaTEX2e