From SmileyFaces:  ''The traditional :) probably doesn't indicate so much that the writer is smiling, but that he expects the reader to smile and recognize what he has just said as good-hearted or a joke. That being said, particularly impolite people can use them to appear respectful when they're really not, as in EraserPhrases? ("with all due respect", etc).''

I normally try to be more explicit, "WithAllDueRespect, by which I mean none at all..."

I'm partial to, "No offense, but I'm about to offend you..."

I think comedian Dom Irrera coined the term.  His favorite is "I don't mean that in a bad way."  It has the advantage of being a suffix.

"I'm not racist but...", This is particularly funny/sad when used in a statement that is certainly discriminatory, but not at all racist.  "I'm not racist, but women don't deserve as much money as men!" or "I'm not racist, but gays don't belong in the millitary!"

"Don't flame me, but..."

"I haven't spent much time reading about this deceptively simple concept, but..."