In case you aren't a member of the tech news obsessed, identica implemented the twitter API. This means that with a simple switch of a string for the API URI, a twitter app can post to identica. Here are the current apps.
For the web, there are many apps to post to identi.ca, like ping.fm, which seems to be rather popular with identicans. You can also post and receive notices via any jabber or GTalk enabled application, like AdiumX for the Mac.
For the Mac desktop, there is a hack to modify the prefs of the shareware Twitterific to work with identica. This should probably also work with other servers running the latest laconica server software. (Locally, I haven't yet deployed the latest as of this moment, but have finished porting the MySQL code to PostgreSQL code and can deploy later today.)
The really interesting options though are the Adobe AIR apps, Twhirl and Posty. I haven't played around yet with Posty, but the Twhirl integration is very nice. It includes an option to have your messages taken from the push of identi.ca's XMPP feed (jabber transport stream) rather than pulled via polling from identi.ca's rss feed. (Here's a really nifty slide share presentation on XMPP streams versus rss feed polling, which talks about the timing and server/network load advantage to using an XMPP stream.).
twhirl interface using the identi.ca search
with button identification via skitch
Now I'm waiting for these apps to place the API URI in to a string that I can change via the preferences, rather than hacking at the commandline like the Twitterific hack. Then you can set up your own microblogging site and have your very own desktop and web apps to post to it or aggregate from it. Until then the federation aspects of the laconica software will be sidelined by the lack of support for the localisation from desktop and web apps, like ping.fm and friendfeed.