Wikipedia article on finite state machines with links to articles about pushdown automata, linear bounded automata and Turing machines.

Wikipedia article on FSA, Moore and Mealy machines.

A regular expression FSA visualizer that provides interactive visualization of how finite-state automata can be used to match regular expressions.

Course notes from the University of Kentucky with sections on finite state automata, pushdown automata and linear bounded automata.

An essay by David Weir.

A terse statement of important definitions and theorems in this field of study.

Set of slides from History of Computers and Computing with basic information on automata.

Notes, small essays, explanations, reading lists. By Cosma Rohilla Shalizi.

A brief survey of finite state automata, pushdown automata, linear bounded automata and Turing machines.

Intuitive definitions of automata from the more complex Turing machines to the simpler finite state automata.