ICD Search Tool
http://www.cms.hhs.gov/icd9ProviderDiagnosticCodes/07_summarytables.asp
http://www.icd9data.com
http://www.aapc.com/icd-10/codes
ICD-9-CM Official Guidelines
http://www.cdc.gov/nchs/data/icd9/icdguide09.pdf