From time to time I get introduced as a "signatory of the Agile Manifesto". Usually what they mean is that I'm an author of the Manifesto for Agile Software Development, and thus one of its initial signatories. But actually there are many more signatories than the 17 authors, when I last looked the count was up to 10,104. If you're so inclined you may join that list.
After the Snowbird weekend Ward put up a web-site for the manifesto, at that point he suggested
We've already been asked to accept more signatures. I'd be willing to supervise (audit) the collection of names through the site. These could become a third page of the site. I would probably collect them until we had dozens or even hundreds of names.
Ward put the original manifesto page up in late Februrary, shortly after the snowbird meeting, hosted on his own server - the same one that ran the original wiki. It was at the URL agileAlliance.org, which Ward later donated to the agile alliance using agileManifesto.org for the manifesto. That original site just contained the values, we worked on the principles over the next month or so. They were finalized and published in April.
The facility for people to sign the manifesto was added in Octoboer. Chet Hendrickson was the first to sign at Wed Oct 10 20:10:20 CDT 2001. Each signatory supplies a name, a URI, and a short statement. Since it went live we've reached two orders of magnitude more than Ward's early estimate. Ward still audits the signatures himself with the help of some ruby/cgi code that Prag Dave whipped up all those years ago.
In a recent fit of curiosity I asked Ward for some data on the signatories. He did a bit of munging through his logs and I did some more munging on the data he gave me. Here's a plot of the number of signatories per month since the manifesto became signable
As you can see (you'll probably need to open the image to see it properly) the manifesto had a definite increase in monthly signers from 2004 to 2008. I think you get a better sense of this by looking at the number of signatories per year.
The most recent activity on the manifesto has been its translation currently coordinated by Henrik Kniberg. The first translation, to Swedish, was published in February 2010. As I write this there are a total of 22 languages done and another 15 in progress. Each translation sparks a lively debate and discussion.
There's never been any particular push to add signatures. People have just signed up as they have come across the web page. Part of me doesn't want to change that with this post - but it's too interesting a tidbit.