Public Access to Court Electronic Records (PACER) is an electronic public access service that allows users to obtain case and docket information online from federal appellate, district, and bankruptcy courts, and the PACER Case Locator. PACER is provided by the Federal Judiciary in keeping with its commitment to providing public access to court information via a centralized service.
BloombergLaw has a docket searching system that is much easier to use.
BloombergLaw is really picky about formatting for docket numbers. Click on the question mark to see examples.