C#

string[] my = new string[]{ "a", "b", "c", "d", "e" };

// Find the start index of the second column:
int midPoint = (my.Length / 2) + (my.Length & 1); 

for (int i = 0, j = midPoint; i < midPoint; i++, j++)
{
    Console.WriteLine("{0}\t{1}", my[i], (j >= my.Length ? null : my[j]));
}