First, I'm new here. Just got a Nexus One a couple of weeks ago and was somewhat disappointed that there wasn't an official Yahoo Messenger app(everyone I know uses it). Anyway, I just found the official Yahoo Messenger just showed up in the Market. Yahoo Search and Mail are there as well but I'm not sure if they are new or not. Absolutely loving it so far.
Yahoo! Messenger for Android
Yahoo! Messenger for Android