I do think about things in terms of 'musical moods' when I'm choosing what album to put on next. I kind of think in terms of ''I feel like something...':
Fast and punky (X-Ray Spex, Yeah Yeah Yeahs, The Horrors etc)
Banging dance (Trade CDs, acid techno etc)
Chilled dance/crossover (Massive Attack, chilled out mixes, Lamb etc)
Funky dance (Tech house, breakbeat, electroclash)
Melodic crunchy rock (Smashing Pumpkins, Muse, QoTSA)
Poppy (Ben Folds Five, The Bees, Pop Levi)
Punky pop (Le Tigre)
Indie (Sleeper, The Bravery, Smiths)
60s/70s (Hendrix, Beatles, Stones)
Classical