Twitter has never been an ideal two-way conversation tool. It's hard to keep track of back-and-forth communication between users, particularly when you're not actually part of the discussion but still interested to know what's being said.
Dialogues in Twitter mashup lets you restore conversations. Just post there an URL (or simply status ID) for any public status (posting in Twitter), published in reply to some user and see the whole conversation. It looks so, for example. Also you can use an appropriate bookmarklet from our suite.