Vertically collapse text
Pyth, 10 bytes

jb_.T.T_.z


Try it online in the Pyth Compiler/Executor.

Idea

We can achieve the desired output by applying four simple transformations:


Reverse the order of the lines:

Golf
Code
&amp;
Puzzles
Programming

Transpose rows and columns:

GC&amp;PP
oour
ldzo
fezg
lr
ea
sm
m
i
n
g


This top justifies, collapsing the original columns.
Transpose rows and columns:

Golflesming
Coderam
&amp;uzz
Prog
P

Reverse the order of the lines:

P
Prog
&amp;uzz
Coderam
Golflesming



Code

        .z  Read the input as a list of strings, delimited by linefeeds.
       _    Reverse the list.
   .T.T     Transpose the list twice.
  _         Reverse the list.
jb          Join its strings; separate with linefeeds.