I implore you to discuss the greatest band ever: Pink Floyd.
I thought it kind of odd that there is a Prog/Psych forum but no Pink Floyd thread. Sacrelige! Maybe they are a bit too mainstream when compared with the likes of Spooky tooth, Gentle Giant, and Caravan.
But this dosent have to be a thread about Dark Side, We can dig a little deeper in to Atom Heart Mother, More and Ummagumma, among others.
My top 3 albums:
Atom Heart Mother
Obscured By Clouds
Animals
Top 3 Songs: (these change often)

Echoes
Cymbaline
Dogs