Here are the top five free Service Desk Apps you might be interested in.

Top Five Free Service Desk Applications
There are many service desk apps on the market, but not all of them free. Here are the top five free service-desk applications.
User Voice
It is the best software and can be used in product outlets that receive tons of feedback about their products. They need a solution that will help them rank and process the feedback. You can eliminate hundreds of suggestions that are similar.
This help desk application has a few key features. It suggests search terms to users as they type, and integrates with Facebook. This software helps Customer Support representatives understand where they can improve with a feedback report.
This software includes all the features you would expect from a full-sized help desk software tool. It also has a ticket filter tool that routes all tickets received via email and phone calls to the appropriate customer service representative. It also has an auto-responder feature that allows you to set up the work flow according to the ticket type.
Its key feature is that the agent can add logo, image, or video to tickets. There is also an unlimited SLA agreement.
This software allows you to be notified via email whenever tickets are created or modified. This software allows you to sort tickets based on their status (new, open, escalated or pending), as well as the date.
This software allows you to handle more requests, which reduces errors and maximizes the efficiency of your representatives.
It is a Java-based help desk software that provides the interfaces to manage tickets with notes and solutions. This software will display previous tickets and any solutions to existing tickets whenever an agent creates a new ticket.
PHP Helpdesk
It is an application that allows you to archive and follow up on help-desk events. It assigns an ID (unique number) to each issue. This application allows you to prioritize tickets based on urgency, since not all issues are of equal importance. Each ticket is assigned to a team person manually or automatically. The customer can communicate with the team member via web interface, attach files and add notes to the tickets. Customers are notified via email when staff responds to their tickets and the issue has been resolved.