I've been trying out micro-blogging through Identi.ca recently. (I'm jpichon, if you're curious.) I find their integration with XMPP both awesome and handy, so here's a quick guide to setting it up and using it, if you haven't given it a try yet.
Start by adding email@example.com to your buddy list. Then, log in to your Identi.ca account, go to Connect -> I.M. and enter your XMPP enabled address. They say any Jabber or GTalk account will work, I'd be surprised if it didn't work with any XMPP account.
Authorise firstname.lastname@example.org when it asks to add you, and tadam! You are set to send and receive updates, depending on the options you selected on that initial Connect -> I.M. screen.
How to use it
Don't trust the Identi.ca help page as it appears new commands have been added since it was last updated. If you open a chat with your new email@example.com buddy and type 'help', you'll see the following menu:
(12:34:56) firstname.lastname@example.org: [Identi.ca] Commands: on - turn on notifications off - turn off notifications help - show this help follow <nickname> - subscribe to user groups - lists the groups you have joined subscriptions - list the people you follow subscribers - list the people that follow you leave <nickname> - unsubscribe from user d <nickname> <text> - direct message to user get <nickname> - get last notice from user whois <nickname> - get profile info on user lose <nickname> - force user to stop following you fav <nickname> - add user's last notice as a 'fave' fav #<notice_id> - add notice with the given id as a 'fave' repeat #<notice_id> - repeat a notice with a given id repeat <nickname> - repeat the last notice from user reply #<notice_id> - reply to notice with a given id reply <nickname> - reply to the last notice from user join <group> - join group login - Get a link to login to the web interface drop <group> - leave group stats - get your stats stop - same as 'off' quit - same as 'off' sub <nickname> - same as 'follow' unsub <nickname> - same as 'leave' last <nickname> - same as 'get' on <nickname> - not yet implemented. off <nickname> - not yet implemented. nudge <nickname> - remind a user to update. invite <phone number> - not yet implemented. track <word> - not yet implemented. untrack <word> - not yet implemented. track off - not yet implemented. untrack all - not yet implemented. tracks - not yet implemented. tracking - not yet implemented.
(As a side-note, if you see me saying 'help' on Identi.ca, I'm not in trouble, I probably fat-fingered the command. Ignore!)
These are all the cool commands to do basic micro-blogging tasks from the comfort of your IM client, as well as a few house-keeping tasks. I particularly like the commands using ids: Identi.ca has a feature I find very nice, the link "in context" under notices that let you follow the flow of a conversation (see an example). Replying / repeating with id lets you preserve this link.
For a bit of context (heh!), when you have your IM client open and someone you're subscribed to writes a notice, you'll see something like this:
(21:23:51) email@example.com: CoolKid789: Hello, world! 
12345 is the notice id, so you still don't need to open a browser. Usually, both the id and the person name appear as hyperlinks, if you'd like quick access to the web view. To preserve the link, I would reply:
reply #12345 @CoolKid789 OHAI!
The actual notice posted (and associated character count) will start from @, and the 'in context' information will be preserved.
Something to watch out for: When I initially tried this, I kept getting a "Message too long" error, even when writing very short notices. It turns out that when I was copying the ids in my IM client, Pidgin, I was also copying the url for the initial notice, even if I couldn't see it. Right-click -> Reset formatting in the text area and the problem is solved. Have fun!