Once upon a time (1999/2000), you couldn't get away from Moby. His music was perpetuated through adverts, since every song on his album Play had been licensed for commercial use, and as a result buyers practically knew the whole album before they'd picked it up off the shelf. Nowadays, however, you're hard pushed to see any adverts using one of those songs. This prevalence is perhaps a sign of how dated the material is.
The same cannot really be said for the music of folk-minimalists Penguin Cafe Orchestra. Their music is often found in television programmes and adverts, many have heard them without consciously knowing it, often producing an "Oh, this is that music!" response. And yet it is 20-30 years since these pieces were recorded and 12 since the group ended after the passing of leader Simon Jeffes. This likely stems from their timeless nature; they seem like arrangements of traditional pieces despite being original compositions, and they are never used as part of a period aesthetic.
First up, Music For A Found Harmonium, as performed here on a BBC broadcast in 1989. A Celtic-leaning cover of this by Patrick Street has been used recently on MFI adverts, and a BBC advert used the abhorrent dance remix by Steve Mac, a producer-of-choice for Simon Cowell and Louis Walsh.
From the same broadcast, Perpetuum Mobile, which has been used for Hewlett-Packard, Knorr and HP sauce.
And finally, Telephone and Rubber Band (here played over reversed footage from Fritz Lang's excellent Metropolis), which seemed destined for use by One2One/T-Mobile.
As a postscript, here is another piece of music that is also unconsciously familiar to many. If we think of big country houses onscreen, the music we hear is inevitably Michael Nyman's Chasing Sheep Is Best Left To Shepherds from the Peter Greenaway film The Draughtsman's Contract.