Twitter timeline feature. Like Twitter's own search, Google's Twitter timeline can tell you what people are saying about your search term right now. Google's done one better, though, by indexing tweets back to the beginning of time (well, the beginning of Twitter, anyway), and displaying an activity graph that shows you when tweets about your topic spiked.
The implications of indexing every tweet and making them all searchable are pretty huge. I'm excited to be able to go back and find some of the funny tweets I wrote a couple of years ago, but you might not be excited that people can find all the mean things you said about your boss before he discovered Twitter. Don't worry, though, deleting a tweet will wipe it out of Google's results, too.
It's interesting that Google made this move the day after Twitter announced Promoted Tweets on its search page. Can you use Google to skip Twitter's search and thereby skip its ads? On the other hand, it makes sense to launch a new Twitter feature on the opening day of Twitter's Chirp Conference for developers. It'll give them something to talk about in San Francisco.