I have included below my 5 modifications that I have recently setup on my phpBB3 site. In addition, I have included below the additional modification that I got from Yernur that I also chose to setup on my phpBB3 site. 

Modification Name: Create users
URL: http://www.phpbb.com/mods/db/index.php?i=misc&mode=display&contrib_id=2964
Description: Allows you to create users to your phpBB3 site without having them directly register to your site by creating the user ids themselves. This was an easy to follow modification.

Modification Name: Google Search Box
URL: http://www.phpbb.com/mods/db/index.php?i=misc&mode=display&contrib_id=11615
Description: Places a checkbox underneath the search box of the main page that allows you to also search using the Google search engine. This was a straight forward installation.

Modification Name: Add snow to your forum
URL: http://www.phpbb.com/mods/db/index.php?i=misc&mode=display&contrib_id=11495
Description. Adds a snow effect to your phpBB3 site. This was a fun and cool modification to add the site without much effort.

Modification Name: Prime Login Return
URL: http://www.phpbb.com/mods/db/index.php?i=misc&mode=display&contrib_id=12155
Description: Returns the user to their previous known location on your phpBB3 site after he/she has successfully logged into your site.

Modification Name: Karma
URL: http://www.phpbb.com/community/viewtopic.php?f=70&t=559069
Description: Add Karma rating widget to your phpBB3 site in the forum message posts that are made by users. You can give positive or negative karma based on posted comments. This was the most tedious and longest (+2 hours) modification from all the modifications that I have done so far.

Modification Name: Expand Categories
URL: http://www.phpbb.com/mods/db/index.php?i=misc&mode=display&contrib_id=9215
Description: Allows the user to expand and collapse categories if there are too many to navigate through. I got this modification from Yernur.