Print a Tabula Recta!

Vim, 25 23 bytes

:h<_↵jjYZZP25@='Ypx$p'↵

Where ↵ is the Return key.

:h<_↵                       Open the help section v_b_<_example.
     jjY                    Copy the "abcdefghijklmnopqrstuvwxyz" line.
        ZZP                 Close this buffer and paste in ours.
           25@='     '↵     Run these commands 25 times:
                Yp          Duplicate line and move to column 1 of new line.
                  x         Cut the first character.
                   $p       Move to the end and paste.

EDIT: lowercase is okay, so I can save two keys.

05AB1E, 6 5 bytes

Thanks to Downgoat for saving 1 byte. Code:

ADv=À

Explanation:

A      # Push the lowercase alphabet.
 D     # Duplicate it.
  v    # For each in the alphabet...
   =   #   Print without popping and with a newline.
    À  #   Rotate 1 to the left.

Uses the CP-1252 encoding. Try it online!.

Python 2, 59 57 53 bytes

a=range(65,91)*27
a[::-27]=[10]*26
print bytearray(a)

Thanks to @xsot for -4 bytes!