Shoutbox

I am aware of that fact, SIMP is one, it uses a proxy, and as such, it has to be running all the time, and it takes about 2 seconds to start a convo with someone who doesn't have it, because it automatically tries to enable encryption. There is also Encrpted messenger 3 (available from mess.be) But it adds extra windows and stuff on the side so you can see the messages in their decrypted form, basically I couldn't find a program that I was happy using because of
a) the impracticality of using it to speak to people who dont have it (SIMP) or
b) the crap interface of using it to speak to people who do have it (Encrypted messenger 3, and my contact couldn't get it to work)

But also, a Plus! plugin would be MUCH easier to distribute and set up.