Here are some classic trance and house vocal tracks:
Ascension - Someone (Original Vocal Mix)
BT - Remember (Original Mix)
BT - Mercury & Solace (Original Mix)
BT - Dreaming (Original Mix)
Cass & Slide - Perception (Vocal Mix)
Chicane - Autumn Tactics (The Thrillseekers Club Mix)
Coast 2 Coast - Home (Dj Tiesto Remix)
Delerium - Silence (Dj Tiesto "ISOS" Remix)
Delerium - Innocente (Dj Tiesto Remix)
D:Fuse - Everything With You (Vocal Mix)
Dj Tiesto - In My Memory (Gabriel & Dresden "Elephant Memory" Remix)
Dumonde vs Lange - Memory (Original Mix)
Everything But A Girl - Missing (Todd Terry Mix)
Evoke - Arms Of Loren 2001 (Ferry Corsten Remix)
Iio - Rapture (Deep Dish Remix)
Iio - At The End (Scumfrog Mix)
Jan Johnston - Flesh (Dj Tiesto Remix)
Jan Johnston - Unafraid (Paul Oakenfold Mix)
Kirsty Hawkshaw - Fine Day (Mike Koglin Mix)
Lange - Follow Me (Original Mix)
Marco V - I Feel You (Original Mix)
Oceanlab - Sky Falls Down (Original Mix)
Paul Oakenfold - Southern Sun (Dj Tiesto Remix)
Riva - Time Is The Healer (Armin van Buuren Remix)
Sander Kleinenberg - Sacred (Vocal Mix)
Solar Stone - Speak In Sympathy (Original Mix)
Solid Sessions - Janeiro (Armin Van Buuren Remix)
Sultan - Night Visions (Vocal Mix)
Three Drives On A Vinyl - Greece 2000 (Original Miro Vocal)
This is the real stuff, probably the stuff you won't hear at your local clubs if you're in the states. Unless you're maybe in Miami or LA, where these good acts come. The songs I listed are from 2003 and older. Most are older. Get familiar with these and then find new ones. Stay away from acts such as Lasgo, Ian Van Dahl, Scooter, Louie DeVito, Dj Sammy and etc. Those acts are "cheese" and commercial shit that is not innovative and it is ruining the industry. Have fun.