Dennis van der Stelt just posted about how to use LINQ to access data from in an Excel document:

string filename = @"C:\myfile.xls";
string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;" +
"Data Source=" + filename + ";" +
"Extended Properties=Excel 8.0;";
OleDbDataAdapter dataAdapter = new OleDbDataAdapter("SELECT * FROM [Sheet1$]", strConn);
DataSet myDataSet = new DataSet();
dataAdapter.Fill(myDataSet, "ExcelInfo");
DataTable dataTable = myDataSet.Tables["ExcelInfo"];
var query = from r in dataTable.AsEnumerable()
            select new
            {
                RelationNr = r.Field<double>("RelationNumber"),
                ClientName = r.Field<string>("ClientName"),
            };
foreach (var item in query)
{
    Console.WriteLine(item.ClientName);             
}