OTR is an encryption layer for Instant Messaging which provides encryption, authentication, deniability and forward secrecy.
A pidgin plugin for Twitter. So Twitter messages can be get / set via pidgin.
A pidgin plugin for Facebook Chat, it adds Facebook as a protocol to pidgin accounts.
A pidgin plugin for Skype. If you have skype installed (and running) you can use pidgin to chat with friends. Genius. All the other pidgin plugins also work (off the record messaging, spell check, etc). Sweeeeeet.
Bot Sentry is a Pidgin (libpurple) plugin to prevent Instant Message (IM) spam. It allows you to ignore IMs unless the sender is in your Buddy List, the sender is in your Allow List, or the sender correctly answers a question you have predefined.