I have been active in many social networks lately, and have been trying to get into Social media to learn how it works and helps in web promotion and development.
So, twitter, facebook, linkedin(for business networking) were the one which i was lately browsing and using to build up my profiles, and now have to add a couple to the list –
Friendfeed did not impress me much but Plurk is cool.
Plurk is also a micro-blogging service like twitter, but with some cool features and Karma!
It takes similar small updates concept from Twitter, and adds a time zones and karma feature to show how active you are there.
Frankly speaking -
Plurk is better than Twitter in a case that multiple replies like mini-threads can be made and discussions can continue in the very simplest ways. And it is more easier for communication.
People at plurk have really done well in making the site, and it has come with awesome concept. And your karma increases or decreases depending on how much active you are.