I’ve started using Twitter (sorry only in dutch), the nice thing about this service is the free API. Thanks to this API there are many ways to integrate twitter in your websites and your life.
For using Twitter on your mobile or desktop check out this site for a large list of Twitter apps. I have a Windows mobile based phone (Samsung Omnia) and I use Tiny Twitter. And on my Ubuntu desktop I use gTwitter.
I have a Flickr account and want to connect this to Twitter. This way I can mail my photos from my mobile to Flickr and automatically post this on Twitter. I was searching for a service like this and found Snaptweet. This did indeed what I wanted, but it was taking 10-20 minutes to see the photo on Twitter. That’s to long for me.
Next service I found was Twittergram, but they have a problem with the connection to Twitter so I couldn’t test it.
For now I’m using Twitpic, they also offer a email address to send your pictures.