I am having difficulties in trying to break apart sugar which I have
put in a clear glass container with a screw on lid.  I want to be able
to use the sugar, but it is all clumped together and I am afraid if I
start hacking away at it I will break the glass container.  Is there
any way to get the sugar out and be able to use it without potentially
breaking the container?  (I also have another container with the same
problem, but with brown sugar).
Thanks.

Are you just trying to save the jar?  You could melt the sugar by
placing the jar with no lid in a pot of simmering water.

If you want to keep the crystalinne nature of the white sugar you need
to keep moisture out...this can be done with tight seals or silica gel
packs (like you get in your new shoes!)

You could put a little water in the top of the jar and scoop out that
bit...repeat until empty then let the water evaporate from the sugar
in a bowl, pound with meat tenderizer or give a quick zip in a food
processor to restore granularity.

Put open the jar in a metal pan filled with a couple inches of water. 
Put the whole thing in an oven at 200 degrees for about 4 hours.  The
Joy of Cooking has lots of tricks like this...

     -welte-ga

How can hard brown sugar be softened?

Here are several suggestions: 

Place a piece of foil or plastic wrap directly on the sugar and set a
piece of dampened paper towel on the foil. Cover the container
tightly. The sugar will absorb the moisture and become soft. Remove
the foil and paper when the paper is dry.

Place a slice of fresh bread in the container with the brown sugar.
Cover tightly and leave for 1-2 days. When the bread is dried out,
remove it.

To soften brown sugar quickly, heat it in a slow (250 to 300 degrees
F.) oven for a few minutes.  Measure it as soon as the sugar becomes
soft as it will harden again when it cools.

If brown sugar hardens, let it stand overnight in a sealed jar with an apple slice.

==========

How can I soften hard white sugar? 
 
Sugar hardens when it is exposed to moisture, like high humidity, and
then the surface dries. Break the hardened sugar into manageable
pieces with a meat tenderizer or heavy mixing spoon. Toss the pieces
into a food processor or blender, and blend until smooth.