If you don't mind writing a very short, reusable function, the ConvertAll Extension Method might help:
http://msdn.microsoft.com/en-us/library/73fe8cwf.aspx
EDIT:
This would work too
List intList = new List() { 1, 3, 4 };
object[] objectList = intList.ConvertAll(item => (object)item).ToArray();