TTFN: Ta Ta For Now
SWAK: Sealed With a Kiss
FYAO: For Your Eyes Only
SIT: Stay in Touch
TPTB: The Powers to Be
SYLA: See You Later….Alligator ..lol

If still confused, here is more..:))

http://www.webopedia.com/quick_ref/textmessageabbreviations.asp

Salam