Gente

• David Arbour's Web Page is a great reference work.  If you are looking for
  process control information go straight to David's site.
• John Shaw's Web Page - Mr. Shaw is an expert in his field.  If you are interested in PID or loop tuning, this site is for you.
• Patrik Johansson's PI loop tuning program - Fill in the process gain (Kp), process time constant (T), process dead time (L), and controller time scan (Ts) and the program calculates controller gain and integral.  Choose from several popular tuning methods!  
• AlibagCity.com by Prashant N. Mhatre is a very cool site.  This link points to his Process Control section, but his web site is varied and fun to explore (if you can tolerate the plethora of geocities' popup ads)