http://www.filehelpers.net
The FileHelpers are an easy to use .NET library written in C#. Is designed to read/write data from flat files with fixed length or delimited records (CSV). Also has support to import/export data from different data storages (Excel, Access, SqlServer)
Code on GitHub: https://github.com/MarcosMeli/FileHelpers
db4o is the world's leading open source object database for Java and .NET. Leverage fast native object persistence, ACID transactions, query-by-example, S.O.D.A object query API, automatic class schema evolution, small size (http://developer.db4o.com)