"Blessed be" is a greeting used primarily by Wiccans, but also by some of us other Neopagans. From what I can tell, it's usually just for those who practice magick and/or follow the wheel of the year (calendar), but the "fluffy" poser Wiccans/Neopagans go around spouting it to all and sundry.

(Also, the only person I've ever said "Salve" to is my high school Latin teacher and fellow classmates. XD)