William_the_Bloody

For Portishead start with Dummy play through all the tracks because I find a lot of the better stuff is at the end. Their second self titled release is worth checking out as well.

After that check out the Machine Gun song of their third album & then some of the singles they've released over the last five six years Tear Drop ect.

You will also want to check out the first three Massive Attack albums, Blue Lines, Protection & Mezzanine, as well as Tricky's first two albums, Maxinquaye & Pre Millenium tension.

If you want something more accesible and groovy I highly recommend Morcheeba's first album, Who can you trust, as well of the second release and some of their off the beat & path expermintal stuff.

If the above is not for you, I would simply write the genre off at that point. It is mellow downtempo music, so if your 21 and under it may be a bit hard to swallow.

If you want to dig futher look at what ProxyNOM has suggested. You might also want to look at Lamb, Air, Groove Armada & Saltillo & Audiac. Hope this helps, cheers.