Build a Robot for Under $50
Detailed introduction to robot building with step-by-step information on the chassis, drive train, controller, and sensors.
http://lcamtuf.coredump.cx/robot.txt

Introduction to ISA Server 2000 by Larry Hunt
Step by step tutorial on how to install and configure ISA Server 2000, ICS, domain controller and DHCP.
http://larryhuntjr.tripod.com/

Simple Step llc
Manufactures of OEM stepping and stepper motion control products for the instrumentation, automation and robotic industries. Stand alone units comes complete with translator, driver and I/O.
http://www.simplestep.com/

TLA Microsystems (NZ)
Little Step-U: a small, serially controlled stepper motor controller.
http://www.tla.co.nz/lit_step.html

step
C source code for a Linux stepper motor controller that can control up to 3 unipolar steppers through a PC parallel port. Free Software licensed under the GNU GPL.
http://communico.polito.it/gueli/step/

PID controller design and tuning on Internet
PID controller laboratory providing free interactive applets for robust PID tuning, design and loop simulation based on known or unknown process model
http://www.pidlab.com

HARDI sprayer Controller and monitor
HARDI products include field sprayers, liftmounted sprayers, self propelled, orchard and wine sprayers, handheld
http://www.hardi-international.com/Product_and_Solutions/Monitors_and_Controllers/default.htm

ControlSim - Spreadsheet based simulation of PID controller and process
ControlSim is a simulation of a PID controller and a simple process model used for training and practice in controller tuning, for purchase and download from site.
http://www.jashaw.com/ebooks/simorder.html

Automatic Calculus Solutions
Check your calculus homework! Enter your function to get your calculus derivative or integral with each step explained, automatically and fast.
http://www.calc101.com/

Tuning a PID Controller
Describes the different types of controller. Addresses efficiency and stability aspects.
http://www.newportus.com/Products/Techncal/techncal.htm