Chris Messina, founding father of the the ever-popular (and sometimes not) Hashtag, has proposed a few more syntax specific ways of doing things on Twitter. Chris is suggesting that we use /via instead of (via @cdevroe), /by for quote credits, and /cc for carbon-copying messages to specific people on Twitter.
Chris gives good examples for each of his suggestions so if you have no idea what any of the above means I suggest reading his post.
I like these suggestions but I don't believe /via will hold up well. RT @username may end up going away with Twitter's new Retweet feature rolling out. And typically /via @username would be used in those circumstances. I could be wrong though.