Surround a string with hashes I've already made this in Python, but it seems that it could be shortened a lot:

txt = input("Type something.. ")
c = "#"
b = " "
print(c * (len(txt) + 4))
print(c, b * len(txt), c)
print(c, txt, c)
print(c, b * len(txt), c)
print(c * (len(txt) + 4))


So if the user types:

Hello World


The program prints:

###############
#             #
# Hello World #
#             #
###############



Fewest bytes wins—and of course, the answer can be written in any language.
CJam, 22 20 bytes

qa{4/3*' +f+W%z}8/N*


Test it here.

Explanation

How do you wrap a 2D grid of characters in one layer of spaces (or any other character)? Correct: four times, you append a space to each line and then rotate the grid by 90 degrees. That's exactly what I'm doing here with eight rotations: four for spaces, four for #:

qa      e# Read the input and wrap it in an array, to make it a 2D grid.
{       e# Execute this block for each value from 0 to 7.
  4/3*  e#   Divide by 4, multiply by 3. Gives 0 for the first four iterations and
        e#   and 3 for the other four.
  ' +   e#   Add the result to a space character (space + 3 == #).
  f+    e#   Append this to each line of the grid.
  W%z   e#   Reverse the lines, then transpose the grid - together these rotate it.
}8/
N*      e# Join the lines of the grid by newlines.