Most federal courts participate in the Case Management/Electronic Court Files (CM/ECF) system called PACER (Public Access to Court Electronic Records), http://www.pacer.gov. PACER is a fee-based system for searching federal court dockets (currently set at $0.10 per page viewed or printed as of April 1, 2012, but some documents are free under the e-government act). PACER includes case and docket information for all district, bankruptcy, and appellate courts.
Justia Federal District Court Filings and Dockets provides free access to dockets and documents from 2006: http://dockets.justia.com/.
RECAP is an online archive of millions of PACER documents.
Freecourtdockets.com, according to its website, has over 33 million court dockets available.
