Of the albums mentioned so far I like Goldfrapp's Felt Mountain and Portishead's Dummy best. I'ld recommend those two anytime. Now, let's see what I can add.
There's this guy called
Jay Jay Johansson which I like pretty much. (His music that is.
) The music is based on tricky drum beats and he adds his high-pitched voice on top singing slightly melancholic verses in a - to me - slightly sinatra-like manner. it actually sounds a little ironic. maybe not everybody's cup-a-tea.
Then there's Megashira's [ame="http://www.amazon.de/At-Last-Megashira/dp/B00005JA1Y/ref=sr_1_1?ie=UTF8&s=music&qid=1197501807&sr=8-1"]At last[/ame]. More like a drum'n'bass/jazz kind of thingy. Pretty fast.
Next would be
The Cinematic Orchestra. I've got the album "Every Day" and I absolutely love it. Slower stuff, jazzy, with hip-hop influences and a slightly cinematic/sound track feel.
I don't know if this classifies as trip-hop but you might enjoy
De-Phazz's "Death by Chocolate". Every once in a while I listen to this album and it never bores me. It's laid-back, slightly latin, slightly 50-ies electronica style is so unique. At least in my experience ... I don't know any similar sounding album. Not even other stuff from De-Phazz.
Last but not least there's Björk. I don't think I need to say much about her. Again, don't know if she classifies as trip-hop. Prolly she's in a league of her own. And I can understand that not everybody likes her voice. But she's among my all-time favourite musicians.