Find and Remove Redundant Files

Bought my first Mac Desktop about 4 months ago having come from the Windows platform.

So far I am loving the whole Mac experience.

During the last month or so I have been installing various apps, some free and some trial. Some have stayed but a lot have been trashed.

Is there an easy way either through the terminal or a utility that can scan the HD for redundant files and give the option to delta them.

I have been told that unlike windows, I no longer need to worry about defraying or anything like that but I do like to try and keep my system in tip top shape wherever possible.

Thanks.