As I fill out my campaign setting, I am going over the many ways that nations, power groups, and nobles might communicate.
Animal Messenger: This is basically no better than having an expedient carrier pigeon. It's certainly not sufficient for a global messaging system, but it probably is sufficient for communicating within a small region. It doesn't follow the intended recipient around, and isn't always useful in bad weather. An organized system of messenger pigeons do equally well though perhaps at greater cost and trouble.
Sending: Lets you communicate globally, but only by 'tweeting'. It's not particularly useful for complex communication, as its a 5th level spell per 'tweet'. Unless you are rolling in 9th level Sorcerers, you can't run an empire's day to day affairs on this. You can however do really important command and control stuff if you have even one tame spellcaster to help. A great many real world battles are decided by commander's being out of touch with each other. This solves the problem... until you run out of spells for the day.
Whispering Wind: At one mile per level and with the same content limitations as 'sending', this also not particularly useful except for dialing '911'. It also arguably doesn't work if the recipient is in the midst of a hurricane - "What was that? I can't hear you. Oh bugger." But it's on the other hand much more accessible.
What other inventive ways could people communicate in a fantasy setting? Thanks ahead for the replies!
If two high level spellcasters both know the true name of an outsider, they can use that outsider as a 'mail box' by Calling him and asking him to relay a message to X when they next see him. If the outsider is powerful enough to teleport, then they can use it as an expedient messenger that is far more effective than Sending. One can imagine two powerful casters communicating by Lantern Archon. A powerful empire could use a similar mechanism to send not merely messages, but 50lbs of mail and proclamations along with the message - routinely transporting the business of the empire all across the world.
By far the most culture changing magical means of communication is teleport. It's harder to send a message to a great distance than it is to physically transport something the same distance. It's much harder to send a message than it is to just go yourself. (Compare 'Teleport Object' to 'Teleport'). As such, it's going to be hard to beat teleportation networks for communicating over long distances rapidly. If you can get a network of Teleportation Circles, or even just pairs of boxes that switch their contents (via teleport object), you're communication problems between major points of interest are largely solved.
If teleportation isn't accessible, a basic network of riders on fast horses stationed every 20 miles or so with a few fresh horses is going to be hard to beat for daily use unless you can magically enhance it. Hippogriffs or other flying steeds can beat it for speed but not cost. On the other hand, the simple 1st level spell Mount can't beat it for speed necessarily, but makes the cost of such a network fairly trivial and is economically revolutionary once it becomes accessible (which it is as soon as you can mass produce 1st level wizards). You don't have to worry about the cost of feeding, carrying for, rotating, or logistically managing your steeds. Maintaining a messenger network becomes fairly inexpensive for who ever manages it, and the system more than pays for itself by leasing it out for private messages.
The more potent means of long distance travel/communication generally require commoditizing as items, since they usually involve high level spells. The number of 6th level spells (and higher) available to even the powerful is just too low to culture changing unless you turn them into items with at will usage. If you can commoditize them, basically you can have magical telephones, the internet, or anything else you wish to introduce. Whether or not this is a tool of only the rich and powerful depends a lot on how common/cheap you make such items. A crystal ball with telepathy is like 70,000 g.p. which is (assuming a gold based economy) equivalent to like 3.5 million dollars. This puts such items out of reach of your average citizen I would assume.
