I want to alphabetize one of the columns in a spreadsheet

edit

You have to select all the columns that belong together, then select Data - Sort, in the dialog window you then select what column to sort by, you can select a second and third column as well, then the rows will be sorted by those criteria.

Say we have this data.

a   a   a
b   b   b
c   c   c
d   d   d
e   e   e

To produce this result:

a   e   a
b   d   b
c   c   c
d   b   d
e   a   e

...select column B, go to Data -> Sort and choose Current Selection. Then specify to sort Descending.

If, however, you want this result instead:

e   e   e
d   d   d
c   c   c
b   b   b
a   a   a

...then select all three columns, as described in @floris v's answer.