Boomer Radio
My favorite at-work ear candy is  Boomer Radio which streams music onto your computer. It has four "stations", The Acoustic Cafe, Smooth Jazz Favorites, Sweet Soul Music, and Classic Mix. It does play mostly songs from "boomer" coming of age years, but one of the best features of the mix they play for you is that they include newer artists who play music similar in style and spirit to what we grew up with.

I have discovered several new favorite artists thanks to them. While the focus of the site is on boomers, I think anyone who enjoys thoughtfully selected music will enjoy one or more of the different streams available. It is an ad-supported site. Right now, about half of the as are PSAs, and the ads are short, run one at a time, and do not seem to spike the volume to trick you into paying attention.
Pandora does what so many other sites promise, but don't deliver.  It lets you tell it some songs and artists you like, and then analyzes the songs for features and then scans for other songs that share those features.  It goes beyond people who like Willie Nelson often like songs by Waylon Jennings.  The song playing right now was chosen because it has subtle use of vocal harmony, mixed electric & acoustic instrumentation, vocal-central aestetic, and major key tonality.

They've hired musicians to listen to songs and songs (400,000 by 20,000 artists so far) and assign qualities to each song.  Then they ask you to enter a few favorite artists and songs, and based upon the qualities of those songs, play other songs with similar qualities.  It can cross genres and eras, though I've noticed it typically plays songs in batches (4 or 5 country songs followed by 4 or 5 pop-rock songs)

They've just added the ability to look up for each song the qualities they've assigned to it.  And the obligate links to and iTunes to buy the track.  I listen to this a lot on weekends.
Main Websites Page