One of the most well-known producers of this genre is Bonobo. You'll recognize Trip-Hop (also called Downtempo or just plain Chillout) by it's slow, hiphop-influenced beats and the use of various instruments like bass, synths and guitars. The BPM (beats per minute) is rather low and sometimes vocals are used to enchance the mood. Especially female vocals fit really good to achieve this experience for the listener.
Bonobo himself definitely belongs to the more up-beat, happy artists in Trip-Hop. The whole genre was developed in Britain by more moody, dark artists like Portishead, Massive Attack or Tricky. "Days to Come" is my favorite album from Bonobo, his new one is worth checking out too!
Listen to this if you know and enjoy: RJD2, Blockhead, Thievery Corporation, Morcheeba, Tricky, Hooverphonic
Here's a song from the album, hope you enjoy it (one of the tracks with vocals on it, not every track on the album is instrumental):