It's always great to have some older stuff in your collection. Although I'm not so much a fan of the late 70s metal and hard rock, the late 60s are an entirely different matter. Bands like The Beach Boys and some Beatles are just so happy and optimistic; solo artists, such as old school Elton John, are just plain cool.
Of course, one could name drop great artists for hours (The Zombies, The Kinks, Simon & Garfunkel, etc.), but the point is understandable pretty quickly.
Oh, and I'm going through a somewhat humiliating disco phrase, and Peaches and Herb is always a good choice there. The seventies were a period of great music phase as well; Pink Floyd, Billy Joel and The Clash are my favories from then.
As for the eighties...old school Madonna, Sonic Youth, Beastie Boys, Violent Femmes and Blondie get my biggest thumbs up.