Madonna especially in the late '80s/early '90s, and especially with the Sex book.
Emily Haines, the frontwoman for Canadian band Metric, is known for her gyrating dancing during live shows and outfits that display her long legs.
Veronica Varlow, one of Emilie Autumn's Bloody Crumpets, is a burlesque dancer who has the most revealing of the Bloody Crumpets' costumes and will kiss muffins (EA fans), most notably during the "Rat Game" which is mostly her kissing a muffin on stage.
Natalie Horler of Cascada. She's hot the way she is, but then when you take into consideration the lingerie she routinely wears on tours, and the music videos with her NOT WEARING PANTS, the "imagination" runs wild.
Simone Simons of Epica. Aside from appearing naked (albeit tastefully in an allusion to the Eve character in Garden of Eden story) in the cover artwork of their "The Divine Conspiracy" album, just watch the music video for Kamelot's "The Haunting," wherein she guest-stars. If that outfit wasn't her own idea, I'll eat my hat. Oh, and never content to be just another pretty face, her voice is rather pleasant as well.
Norwegian bubblegum star Lene Alexandra is one of the most blatant examples in recent memory. One of her singles is literally a song devoted to her breasts, with a video that consists of roughly three minutes of her posing in increasingly skimpy fetish outfits.
Anne-Sophie Mutter achieved success and fame as a (hot) violinist.
Ofra Harnoy was Mutter's equivalent on the cello.
The video for Eric Prydz's "Call on Me" has a scantily-clad aerobics class doing sexually suggestive moves, which is a turn-on in itself, but the real fanservice girl is the one in the tank-thong.
Shania Twain, who was one of the first major Country Music artists to embrace this trope. In particular, she popularized baring your midriff among a whole generation of both country singers and pop stars, a few years before Britney.
Hippie/space rock band Hawkwind played shamelessly on the charms of their stage dancer Stacia, whose role in the band was effectively to dance to the music, in a spaced-out stoned kind of way, and take her clothes off. As she was over six feet tall with an impressive poitrine, this drew many impressionable fans to the front of the stage.