A lot of Steampunk takes place in the latter half of the 19th Century, or possibly the very early days of the 20th. As such, one of the things that takes prominent position -- especially for those stories in the 1890s/1900s -- is the concept of improved mass communication. In The Difference Engine by William Gibson and Bruce Sterling, which takes place in the 1850s, mass communication innovation takes the form of a machine that can slap handbills up on walls while the worker rides in comfort inside the body of the machine.
In terms of historical innovations, there are several inventions that improved mass communications far beyond what it was for hundreds of years. These include the telegraph, the radio, and improved printing presses as some of the primary changes happening in the 1800s. In the early portion of the 1800s, we also see the invention of the postal system in Britain and the first stamps issued in 1840 -- invented by a schoolmaster named Rowland Hill. Hill was also the first one to design a system where the price of post was determined by weight instead of size.
Samuel Morse invented the electrical telegraph in 1837 while working at New York University as an artist. Yes, Samuel Morse was an accomplished portrait painter, and worked at NYU teaching students how to paint while he also perfected his design for the telegraph. He would eventually receive patents from both the United States government and European nations, and permission to build telegraph lines linking major cities around the world.
In 1843, after receiving permission to connect Washington, D.C., and Baltimore, Maryland, Morse first attempted to lay telegraph wires underground using a machine designed by Ezra Cornell (the founder of Cornell University). However, experiment soon showed that the underground method was unacceptable. Thus, we see Morse deciding to string the wires along poles. Eventually, telegraph wires would become such an integral part of communications in the United States that the Native Americans cut the lines in order to effectively disrupt any and all communication between outposts.
Newspapers also took a quantum leap forward during the mid- to late 1800s. The New York papers realized that the telegraph would change the way people communicated, and were thus early adopters of the technology. Also at this time, we see Robert Hoe's invention of a double-cylinder, steam-powered printing press that exponentially increased the number of broadsheets a newspaper could print. Then, in 1845, his son Richard developed the rotary press. This steam-driven rotary press could produce 100,000 newspapers per hour, a 250 times improvement over traditional hand-cranked presses.
A second, but no less important, innovation that affected newspapers and communication in general was the typewriter. For the first time, people didn't have to rely on hand-written documentation (which as we all know can be nigh unreadable depending on penmanship). In 1868, Christopher Latham Sholes, in collaboration with Samuel Soule and Carlos Glidden, invented the first usable typewriter.
However, the initial machine was prone to mistakes and could break easily. Eventually James Densmore, an investor, bought Soule and Glidden out, and he and Sholes built several machines in succession to perfect the device. Densmore and Sholes offered the machine to Remington in 1873, who would eventually purchase the patents after the machine was perfected.
By the 1880s then, we have the telegraph, the improved printing press, and an actual postal system that are connecting the world. Move into the 1890s and the early 1900s, and we see Guglielmo Marconi and the invention of wireless telegraphy, which would change the communications landscape yet again. (But that's an entirely different post).
Anyway, what does all this mean for Steampunk? Well, it means several things. First off, you've got a vast array of communications technologies to play with. No television yet, but motion pictures arose in the late 19th Century, and Gibson and Sterling had a kinotrope that was used as a rudimentary projector for presentations.
As with most Steampunk then, you can take these inventions -- printing presses, radio, telegraphs, etc -- and turn them into some sort of entertaining blend of mechanics to craft an innovation that makes sense for your world. Case in point: in CALLARION AT NIGHT, there's a device called a Wireless Aetheric Communicator. Could I have called it a radio? Probably, but that wouldn't have been nearly as entertaining.