Yes, I've landed a couple.
My first was via a blog post that a follower retweeted and one of his followers happened to be in the market for a transcriber. The following day I was doing work for the new client - and still do to this day.
The second was more recently and thanks to my 40 tips for using twitter effectively blog post (which had so many retweets I'm still in shock!

) - again someone saw it, looked me up and is now sending me regular work.
I've also had other bits and pieces from twitter friends.
I love twitter, it's my favourite social media tool and I'd advocate its use to all VAs.