Personaly I dont use the BB Messenger, but anyone is free to message over AIM "AndreBSD" (without the quotes of course)... I just keep IM+ running all the time.
FYI: Many people leave their pin in their signature.
Edit: Noticed you had two of the same threads... You really don't need that; and if you check http://www.blackberryforums.com/showthread.php?t=11380
there's already a list