Scenario: Your government is displeased with the communication going on in your location and pulls the plug on your internet access, most likely by telling the major ISPs to turn off service.
This is what happened in Egypt January 25 prompted by citizen protests, with sources estimating that the Egyptian government has cut off approximately 88 percent of the country's internet access. What do you do without Internet?
Step 1: Stop crying in the corner. Then start taking steps to reconnect with your network. Here’s a list of things you can do to keep the communication flowing.
Make your network tangible
Print out you contact list so your phone numbers aren’t stuck in the cloud. Some mail services like Gmail allow you to export your online contact list in formats that are more conducive to paper, such as CSV or Vcard, and offer step-by-step guides on how to do this.
Broadcast on the radio
CB Radio: Short for "Citizens Band" radio, these two-way radios allow communication over short distances on 40 channels. You can pick one up for about $20-50 at Radio Shack and no license is required to operate it.
Ham radio: To converse over these radios, also known as "Amateur radios," you have to obtain an operator's license from the FCC. Luckily, other Wired How-To contributors have already explained exactly what you need to do to get one and use it like a pro.
Set up a phone tree: According to the American Association of University Women, a phone tree is "a prearranged, pyramid-shaped system for activating a group of people by telephone" that can "spread a brief message quickly and efficiently to a large number of people." Dig out that contact list you printed out and follow the steps on the AAUW website to spread the message down your pyramid of contacts.
Enable Twitter via SMS: Though the thought of unleashing the twitter fire hose in your text message inbox may seem horrifying, it would be better than not being able to connect to the outside world at all. The twitter website has full instructions on how to redirect tweets to your phone.
Alex Jones and infowars.com have a telelphone number for people to listen to his radio show by phone in case the internet goes down, or if you don't have internet. The phone in listen line is 512-646-5000.
If you need to quickly send and receive documents with lengthy or complex instructions, phone conversations may result in misunderstandings and delivering the doc by foot would take forever. Brush the dust off that bulky old machine, establish a connection by phone first with the recipient to make sure his machine is hooked up, then fax away.
Getting back online
While it might be relatively easy for a government to cut connections by leveraging the major ISPs, there are some places they wouldn't get to so readily, like privately-owned networks and independent ISPs.
Find the privately-run ISPs
In densely populated areas, especially CBDs and city suburbs there are multiple home WiFi networks overlapping each other, some secure some not. If there is no internet, open up your WiFi by removing password -- if enough people do this it's feasible to create a totally private WiFi service outside government control covering the CBD and you can use applications that run Bonjour (iChat on Mac for example) to communicate with others on the open network and send and receive documents. **needs more clarification
If you are a private ISP, it's your time to shine. Consider allowing open access to your wi-fi routers to facilitate communication of people around you until the grid is back online.
Return to dial-up? o_O
Most wireless routers, PCs, laptops, and even some ultra-mobile devices like cell phones have the ability to become part of an "ad-hoc" network, where different "nodes" (all of the devices on the network) share the responsibility of transmitting data between one another. These networks can become quite large, and are often very easy to set up. If used properly by a tech-savvy person, such networks can be used to host temporary websites and chatrooms. There are many internet tutorials on the internet for ad-hoc networking, so feel free to google some.
Apple computers tend to have very accessible Ad-Hoc functionality built in, including a pre-installed chat client (iChat) that will automatically set up an Ad-Hoc "Rendezvous" chatroom between anybody on the network, without the need for an external service like AIM or Skype. Ad-hoc network hosting functionality is built in to the Wifi menu.
Windows computers have several third-party Ad-Hoc chat applications available (such as Trillian) and setting up an Ad-Hoc wifi network is almost as simple as on a Mac.
Linux operating systems, of course, have plenty of third-party apps available, and most distros have Ad-Hoc network creation support built in.
Get satellite access
You can have very, very slow internet if you have something similiar like an Iridium phone, which would allow you to do dial-up at 2400 baud, which at least gives you email. This will also work when your government has shut down GSM and telephone access, and will work pretty much anywhere on the planet. If you're in the right place, get yourself KA-SAT access (http://en.wikipedia.org/wiki/KA-SAT) which is satellite broadband and will not be routed through any Internet exchange certain local governments may monitor or block (unless that government is part of EU or err... uncle Sam.
Back to the 90s: there do exist short wave packet radio modems. These are also excruciatingly slow, but may get your email out.