SuperWiki is cataloging all the motels the boys have stayed in. By season! Cool.
Here is Season 1, you can find links to the other seasons from there.
"The places Sam and Dean stay during each episode provides a very important backdrop to each episode. Whether they stay in a motel, squat, stay at Bobby's or sleep in the car, it serves to remind us of their nomadic existence. The sets are always excellent, with wonderful attention to detail, the work of Production Designer Jerry Wanek and Art Director John Marcynuk.
The motels in particular have become a signature of the show with each one have a different theme and the set detail often containing in-jokes that only the most dedicated fan will get. Jensen said of the motel rooms: "Jerry Wanek's just a crazy guy, and likes to use his talents when he gets the ability to, and the motel rooms are his passion."
Very geeky coolness.