WFDFF
Chatspeak acronym. Translation: "What Friends Do For Friends." Usually used as an alternative to "you're welcome," with the implied meaning that no thanks are necessary.
{Over IM}
Tim: Thanks for sending me that link, man. You're a life saver.
Bob: WFDFF. :)
Tim: Thanks for sending me that link, man. You're a life saver.
Bob: WFDFF. :)