There are a number of applications around that will let you update all of your social networks at once. The concept is that you write one message & send it to Twitter, Facebook, Plurk etc. They all work basically the same way – you join up, configure all of your networks to talk to the application you’re using & you’re away.
If, like me, you’re in a number of social places, it gets time consuming to post messages to all. These tools are a great help.
I use Ping.fm to post simultaneously to my Twitter, Plurk & Facebook. However I don’t use it all of the time as I’m often posting different information to my various networks. Or perhaps posting something I’ve learnt from one network into another. Ping seems pretty popular amongst the networks I belong to.
hellotxt is similar to Ping. I haven’t joined this one – no use having more update apps than you have social networks! I’ll leave you to decide – or to recommend others you find useful.