Yahoo just demoed its integration of chat and email at the Web 2.0 Summit. This follows on Gmail-GTalk integration, but it adds a few neat features. First, while Gmail lets you respond to an email via chat, Yahoo also lets you do the reverse: respond to a terminated chat by email. (Update: I just figure out how to respond to a chat via email in Gmail; sorry for implying this wasn’t possible.) Also, you don’t have to be signed onto the Yahoo Messenger client, just anything on Yahoo. And chats appear in new tabs, just like emails, rather than being separated. Yahoo Mail has more than 250 million users, but we don’t know how many of them are using the beta interface.