public class Source
{
    public string Value1 { get; set; }
    public string Value2 { get; set; }
    public string Value3 { get; set; }
}

public class Destination
{
    public int Value1 { get; set; }
    public DateTime Value2 { get; set; }
    public Type Value3 { get; set; }
}

void ConvertUsing(Func<TSource, TDestination> mappingFunction);
void ConvertUsing(ITypeConverter<TSource, TDestination> converter);
void ConvertUsing<TTypeConverter>() where TTypeConverter : ITypeConverter<TSource, TDestination>;

public interface ITypeConverter<TSource, TDestination>
{
    TDestination Convert(TSource source);
}

[Test]
public void Example()
{
    Mapper.CreateMap<string, int>().ConvertUsing(Convert.ToInt32);
    Mapper.CreateMap<string, DateTime>().ConvertUsing(new DateTimeTypeConverter());
    Mapper.CreateMap<string, Type>().ConvertUsing<TypeTypeConverter>();
    Mapper.CreateMap<Source, Destination>();
    Mapper.AssertConfigurationIsValid();

    var source = new Source
    {
        Value1 = "5",
        Value2 = "01/01/2000",
        Value3 = "AutoMapperSamples.GlobalTypeConverters.GlobalTypeConverters+Destination"
    };

    Destination result = Mapper.Map<Source, Destination>(source);
    result.Value3.ShouldEqual(typeof (Destination));
}

public class DateTimeTypeConverter : ITypeConverter<string, DateTime>
{
    public DateTime Convert(string source)
    {
        return System.Convert.ToDateTime(source);
    }
}

public class TypeTypeConverter : ITypeConverter<string, Type>
{
    public Type Convert(string source)
    {
        Type type = Assembly.GetExecutingAssembly().GetType(source);
        return type;
    }
}