Normally taking place in the Victorian era, all technology is powered by coal and steam with lots of gears and mechanical glory and everybody wears goggles.
Here is an article on what they consider the top five films/tv shows based on the genre:
In the list, I am only aware of Steamboy which I own.
My favorite online gaslight cartoon is Girl Genius. (Warning: PG rating)
And I waste w-a-y too much time at Brass Goggles, a steampunk-oriented blog that has some of the most awesome photographs I've ever enjoyed.
Enjoy your side trip to a time when men were men and women could build a robot out of kitchen utensils and a teapot.