Enterprise Library for .NET Framework 2.0 - January 2006
http://www.microsoft.com/downloads/details.aspx?FamilyId=5A14E870-406B-4F2A-B723-97BA84AE80B5&displaylang=en
Latest Release (for .NET Framework 1.1): Enterprise Library, June 2005 (patterns & practices Enterprise Library - June 2005)
http://www.microsoft.com/downloads/details.aspx?FamilyId=A7D2A109-660E-444E-945A-6B32AF1581B3&displaylang=en
Enterprise Library for .NET Framework 1.1
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html/entlib.asp