Twitter is now rolling out a new "report abuse" button for individual tweets. This will enable users to more easily report content that they find inappropriate, either because they think it's spam or whether someone is genuinely being abusive to them or some other user.
Previously, it was only possible to report abuse from a user's profile page. This meant that a lot of people gave up on reporting annoying tweets since it disrupted their regular activity too much.
Now, it will be a lot easier to report a tweet and continue scanning your feed or catching up on the tweets of some friend.
The feature is already available to the iPhone app users and will be gradually rolled out to web and Android users, which means you should be spotting it soon, if you don't see it already.