The National Law Journal published a wonderful series of articles chronicling Justice Stevens impact on the Supreme Court. While articles analyze his legacy, top decisions and the future of his seat, my personal favorite is the listing of his most notable dissents.
For more on Justice Stevens, see the following links:
John Paul Stevens Oyez Project Bio
Justice Stevens will not be easily replaced (LA Times)
Justice Stevens will be hard to follow (CNN)
Memories of Justice Stevens from his law clerks (NY Times)
Justice Stevens became great by deeds, not design (USA Today)