Are you a classical music fan? If so you may want to check out KUSC (part of University of Southern California) which streams its broadcst 24 hours a day at http://www.kusc.org/php/Programming/listen.php KUSC is one of the few remaining full time classical music radio stations in the USA.
No FM stations Sorry couldn't find any FM smooth jazz stations that simulcast via the web. However, you can use AOL radio for free and have access to several XM stations. XM Watercolors is my smooth jazz web station!
Actually, there may be more out there than you realize. Peter Ribbens in the Netherlands has a really comprehensive listing of such stations, including about 75 US stations, at classicalwebcast.com. KUSC is one of my favorites, too.