As turmoil over the disputed election in Iran continues, many techs are trying to find ways to help Iranian citizens safely communicate and receive information despite the barriers being established by Iranian authorities. One tactic that even moderately tech-savvy Internet users can employ is to set up a Tor relay or a Tor bridge.
More sophisticated users can skip this paragraph, but for the rest, here's the basic outline. Tor (an acronym of "The Onion Router") is free and open source software that helps users remain anonymous on the Internet. Normally, when accessing websites, your computer asks for and receives a webpage out in the open, a process that exposes your IP address, the URL of the website, and the contents of the site, among other information to third parties. When accessing websites while using Tor, your computer essentially whispers its requests for a website, to another computer, which passes the request on to another computer, which passes it on to another computer, which passes it onto the computer where the website is hosted; the reply returns in the same, chain-message manner. The whispers are encrypted, so that neither outside authorities, nor the computers in the middle of the chain, can tell what is being said, and to whom. And the website itself does not have your IP address either.
Internet users in Iran are using Tor to both (a) circumvent censorship systems and (b) remain anonymous while reading and writing on the Internet. Both are critically important to the safety of protesters, many of whom fear retaliation from the government. Preliminary reports indicate that use of the Tor client in Iran has increased in the days after the contested election.
However, Tor's design relies on a robust network of "volunteer computers" (a.k.a. relays) to pass messages back and forth. This means that the speed and quality of a Tor users' browsing experience relies extensively on the number of volunteer computers there are to pass messages along. This is where volunteers can make a difference -- setting up additional relays improves access for dissident Iranians and other users of the Tor network. The more people who help out, the better and more quickly the network runs. If you're interested in helping out, find and follow instructions for configuring a Tor relay on the Tor website.
Those looking to help fight censorship should also consider providing a Tor bridge. Bridges come into play when an ISP decides to try blocking users' access to the Tor network. (For now, there seems to only be anecdotal evidence of Iran attempting to block the use of Tor. However, Iran has recntly been practicing reactive and centralized blocking, which makes any effective block of Tor far more likely.) The Tor bridge configuration differs from a relay in that your computer does not appear in the public Tor network. Instead, users looking for access to the Internet through Tor can receive your Tor routing information through more private channels, then configure their Tor client to transmit requests through your computer. By not appearing in the public Tor network, your Tor routing information is less likely to end up on an ISP filter and can provide help for a longer period of time -- but recognize that the network needs both relays and bridges.
Tor provides strong protections for its users, but if you plan to use it to access the Net, take time to fully understand its limitations. Check the Tor "Warning" section for more information. You should also consider any limitations that may exist in your arrangement with your ISP.
For understanding the technical conditions of the Iranian Internet, we have found the Open Network Initiative's ongoing research, Arbor Network's network analyses, and the Tor Project's own blog status reports to be informative.