Bar/Club Scene in Seattle?

I’m located in Vancouver. Myself and a few buddies are planning a trip down to Seattle some time in Jan ( I turn 21 ). I was hoping to get some ideas as to where the hot spots are. We are probably looking to do some sort of bar/club crawl and party pretty hard. Where would be some good spots? Keep in mind we are looking for the younger crowd…

I would love to hear about some of your favorite spots and the type of place it is (atmosphere, music, age, style, dress, etc.)

Oh, and how late are your bars open till?

Thanks.