Rush has been my favorite band since I was a kid. Anyone who hasn't yet should watch the Between the Lighted Stage documentary.
A couple dozen songs to check out on Grooveshark (representing most of their albums):
Headlong Flight
The Anarchist
Clockwork Angels
Malignant Narcissism
Far Cry
Earthshine
Driven
Leave That Thing Alone
Bravado
Mystic Rhythms
Middletown Dreams
Marathon
Analog Kid
Subdivisions
Limelight
YYZ
Red Barchetta
Tom Sawyer
Natural Science
Freewill
The Spirit of Radio
La Villa Strangiato
Xanadu
2112