phish - just about any of their long live jams are chill as fuck... album tracks 'you enjoy myself' 'stash' 'the mango song' or 'run like an antelope' are all good, and live versions are even better.

simon and garfunkel
iron & wine
grateful dead - the album 'anthem of the sun' is great. the songs 'uncle johns band' 'franklins tower' 'st stephen' and 'friend of the devil' are all fantastic
theres this band called american football that plays some totally smooth double guitar stuff
explosions in the sky is really awesome intricate stuff
john denver
sufjan stevens
mamas and the papas
sound tribe sector 9
peter paul and mary
tom petty
bob dylan
radiohead
ravi shankar (sitar music. waaay cool)
sigur ros
T.Rex (bang a gong. get it on)
velvet underground