There is a basic set of Facebook "Like" and Twitter "Tweet" buttons that've been in the product since 7.5.6
(August 21, 2010), they're ugly as sin and never really saw any attention once they where added (though we have discussed updating them, but haven't made concrete plans).
You can activate them, and enter your Twitter Account (for any replies), in the Control Panel:
CP -> Display Settings -> General -> Primary Tab -> Topic & Post Page SettingsShow Facebook "Like" ButtonShow Tweet ButtonYour Twitter Account
A likes/kudos/thank post feature is currently in development on my dev site, however there is currently no concrete release date/version for when it'll be available as a stock feature as it is still undergoing testing.