"Syndication" refers to the technology which makes possible automated interchange of information between different websites. The format that indymedia.us and most independent media centers use is called RSS, which stands for Rich Site Syndication. The particular version of RSS most widely supported in the IMC technological ecosystem is RSS 1.0, which is based on a general purpose mechanism for representing structured data in a structured way called RDF, which stands for Resource Description Framework. RDF is usually expressed in XML, a general purpose web standard for structured data exchange through text files. XML looks a lot like a more general version of HTML. RSS 1.0, through RDF, supports using standard vocabularies, invented and agreeed upon by the web community at large, to describe content in more detail; in particular, most Independent Media Centers make heavy use of the Dublin Core, which is a standard set of useful metadata fields one can add to RDF items. By adhering to web standards, IMC geeks across the world have been able to build a decentralized network of computers and codebases which nevertheless are capable of interacting with each other and sharing information.
In practice, syndication works through the production of files called "feeds". A feed is an RSS/RDF file which lists the latest articles published on a site. Another computer can then "pull" this feed by downloading and parsing the file. If this computer pulls multiple feeds from different sites, it is often referred to as an "aggregator". This is how indymedia.us gets features from IMC's across the US.
Indymedia.us tries to syndicate every US-IMC with a working feed of their center column features. We use the network wide list of feeds to determine which IMC's have feeds. The same database also tells us which IMC's are located within the US. Sadly, not all IMC's have a feed listed on this page, and many of the feeds listed do not work (either old links, broken websites, or technical glitches with the format of the feed). As of 6/28/07, here is a list of the feeds we know about and are able to parse:
Indymedia.us doesn't have any power to decide who is and isn't an IMC : there is a comprehensive, democratic, transparent, and global method for doing so through the New IMC Application and Process. Since this is the case, we use the Indymedia Contact Database, which is where the results of the new-imc process are officially recorded, to automcatically get lists of the active IMC's in the US. This is the same database that is used to generate the list of IMC's that appears on most IMC sites across the network.
First, make sure you have a working feed of your features. If you use SF-Active, your feeds should work out of the box, you can see the feeds by going to http://your.imc.here/syn/. If the feature feed listed there doesn't work, try asking for help from the sf-active developers on irc.indymedia.org, #sf-active. If you use Mir, you may need to set up feeds manually if you have an old cvs checkout. First check to see if the file http://your.imc.here/main-features-content.rss exists, if not, hop on irc.indymedia.org, #mir for help. If you use Dada, you should have a feed working, but make sure to set up the cron job that generates it. Email support[-at-]dadaimc.org if you have problems.
Next, make sure your feed is valid. The free service at feedvalidator.org will let you know if your feed has problems, just give it your feed's url. If there are problems, turn to the appropriate source of tech support mentioned in the previous paragraph.
Then make sure your IMC is listed as active in the Indymedia Contact Database, and that region is set to "united states". Finally, make sure that you have a feed registered in the contact database for your center column features, you can see the feeds you've registered here and you can check to see if your feature feed is listed correctly by checking to make sure it shows up in this feed of feeds. If you need help with the contact database (for example if you don't know or have forgotten your imc's password), please have a look at the documentation for the db, email imc-commwork[-at-]lists.indymedia.org, or hop on irc.indymedia.org, channel #tech.
There are a number of problems you may be encountering. A common one is character encodings problems, which will be detected by feedvalidator.org. Often these issues may be transient as a bad character works its way off the list of recent features. The most recent versions of the common imc-codebases will usually fix these issues, but that may require an upgrade. In particular, older versions of SF-Active may have problems with things like Microsoft "smart" quotes.
Another issue, peculiar to older dadaimc sites, is a problem with an unmatched cc:License tag in the syndicate.php file. Details are here, or ask for help at support[-@-]dadaimc.org.
For both mir and dadaimc sites, you need to make sure that the cron job which periodically generates the rss file is turned on. For mir, you should be able to do this in the same script where your other periodic producer tasks are run from. For dadaimc, make sure that the cronmaster job is set up properly. If your feed exists, but seems like it hasn't been updating properly, this is probably the culprit.
If you really are having problems with your feed, please try irc.indymedia.org, channel #us and someone will point you in the right direction to get help debugging your problem.