This one is by memory so bear with me...
The Vegas Lounge format, is not quite Triple A and not quite Nostalgia. They mix the obvious casino-crooners: Sinatra, Dean martin, Sammy Davis Jr., etc. with a cross-over mix from a respectable Triple A: Ben Folds Five, Michael Buble, Norah Jones etc.
Then just out of sheer balls they mix in the rejects from that 1990s swing revival: cherry poppin daddies, big voodoo daddy, Brian setzer etc. The mix is eccentric, but it works. On the same radio dial that spawned Jack-FM, the jump from Etta James to Norah Jones isn't an impasse. The format is young, cool and I like it.
WRDA has had the higest profile by far within the format, but I think KKZZ-AM was actually the first to debut it. Great related article here: http://www.acradio.com/INSIDER_ARCHIVE/mk048.html
There are ONLY three stations braving the waters of this format.
WRDA 104.1 FM St. Louis, MO http://www.red1041.com/
KKZZ, 1590AM Ventura, CA http://www.1590kkzz.com/
WTRI-AM 1520 http://www.vegasradiowtri.com/
*thanks to Scott Tilde for the correction