Pick up a copy of "London Calling". It is a masterpiece. It is hard to find a bad track on the album and most of it has a pretty infectious groove to it. IIRC, it was voted by Rolling Stone magazine as the best album of the 80s (even it originally came out in 1979).
"The Story of the Clash" is a greatest hits collection which is really good. Pet peeve is it doesn't have "Death Or Glory" on it which is one of my favorite tracks by them.