FileHelpers Library
The FileHelpers are a free and easy to use .NET library to import/export data from fixed length or delimited records in files, strings or streams.
The idea is pretty simple: You can strong type your flat file (fixed or delimited) simply describing a class that maps to each record and later read/write your file as an strong typed .NET array. The Library also has support for import/export data from differents storages like Excel, Access, SqlServer, etc.
Go to http://filehelpers.sourceforge.net/
See also these related projects.