ConversationList does a really amazing thing with your Twitter stream. It examines all the conversations you’re having with your Twitter followers and makes a list of out them. When you @reply someone, they are added to the list and when a period of inactivity passes by they’re dropped from the list. The list is updated to reflect changes daily.
Nothing further is required on your part except to approve access for ConversationList to your Twitter account. So if you’re interested in making the connections you want to make on Twitter or keeping up with developing ones, ConversationList is a good start.