http://www.fda.gov/ora/inspect_ref/igs/csd.html
Guide to Inspection of Computerized Systems in Drug Processing. This is from 1983 but is still worth reading as an historical document.
http://www.fda.gov/ora/inspect_ref/igs/gloss.html
Glossary of Computerized System and Software Development Terminology.
http://www.fda.gov/cder/esig/part11.htm
Information on Electronic Signature regulations which came out last year.
http://www.fda.gov/cdrh/comp/swareval.html
General Principals of Software Validation - Draft Guidance. Medical Device Software Validation. Specifically addresses medical devices, but written based upon good software development practices and therefore applicable to other computer software.
http://www.fda.gov/ora/compliance_ref/rpm_new2/contens.html
FDA/ORA Regulatory Procedures Manual, August 1997. Chapter 4 explains the process for issuing warning letters.
http://www.access.gpo.gov/cgi-bin/cfrassemble.cgi?title=21
Title 21 Code of Federal Regulations (21 CFR xx).