Identi.ca, Open MicroBlogging platform
an Open Source, CreativeCommons framework for a distributed network of federated microblogging services.
"How is Identi.ca different from Twitter, Jaiku, Pownce, Plurk, others?
Identi.ca is an Open Network Service. Our main goal is to provide a fair and transparent service that preserves users' autonomy. In particular, all the software used for Identi.ca is Free Software, and all the data is available under the Creative Commons Attribution 3.0 license, making it Open Data.
The software also implements the OpenMicroBlogging protocol, meaning that you can have friends on other microblogging services that can receive your notices
The goal here is autonomy -- you deserve the right to manage your own on-line presence. If you don't like how Identi.ca works, you can take your data and the source code and set up your own server (or move your account to another one)." (http://identi.ca/doc/faq)
"Identi.ca is just over a year old, it’s similar to Twitter and is built on and developed as free software. Specifically it is built on the Laconi.ca micro-blogging application. So yes, that means you can build your own micro-blogging site. Like Twitter, Identi.ca provides 140 characters to tell the world (or those are subscribed to your feed) what it is you want to say. Identi.ca has some advantages over Twitter as well which I believe have sprung from it being free software. Firstly there are groups. While hashtags are supported, Identi.ca also provides groups which are pre-pended with a !. Thus if you post a Dent (a post) containing !linux, anybody who is a member of the !linux group will see your Dent on their home feed. Consider it a cross between a mailing-list, IRC and Twitter. The effect is that on Identi.ca you get a greater number of group conversations than you do on Twitter. Twitter is one-to-many, Identi.ca can be as well but through groups it becomes many-to-many. Thus on Twitter you’ll see more re-tweeting (RT) as a way to propagate tweets. On Identi.ca people will often either post to a group or a Dent will be re-dented to a group.
The second thing about Identi.ca is that it’s not precious about its users. The people behind Identi.ca seem to accept that many of its users will also have Twitter accounts and they’ve made it easy to integrate. Easy to apply settings can cross-post your Dents to Twitter, with the nice feature that you can have it ignore replies you might be sending to Identi.ca users. Now you know what all those !groups are doing in your Twitter timeline. In addition it helps you to find those you follow on Twitter who have Identi.ca accounts. Yes Twitter does similar to Facebook, Facebook does the same with Gmail but Facebook does not do the same with Bebo or MySpace to my knowledge. As you’d expect with a free software-based service, the clients are pretty much all free software as well. Some of them are almost identical in functionality to proprietary Twitter ones — Identifox for example.
Whilst the signal-to-noise ratio on Identi.ca is similar to that of Twitter, the noise is often of more interest
The last thing I want to say about Identi.ca is that because it’s not so well publicised it attracts fewer noise-makers. These would be the users that exist — or so it seems — purely to advertise the latest get-rich-quick scheme or other snake-oil. Thus on Identi.ca you could say that whilst the signal-to-noise ratio is similar to that of Twitter, the noise is often of more interest than Twitter. Because of its free software heritage, Identi.ca attracts a higher proportion of free software supporters and supporters of other freedoms." (http://www.freesoftwaremagazine.com/columns/identica_how_free_software_can_drive_social_networking_revolution)