Most web hosting billing scripts like WHMCS, ClientExec come with integrated support ticket system. But not all web hosting companies uses these paid billing scripts and want a good free support ticket system script.

Below is list of few good free support ticket system script.

• Trellis Desk : Trellis Desk is a powerful and robust help desk solution for your business. Improve your company's service by allowing your customers to quickly and easily submit support tickets to your team. Trellis Desk sports a range of advanced features that enable your business to handle customer support more efficiently. Plus, it's completely free – you'll never have to pay any license fees to use Trellis Desk.
• osTicket : It is a widely-used open source support ticket system. It seamlessly integrates inquiries created via email, phone and web-based forms into a simple easy-to-use multi-user web interface. Manage, organize and archive all your support requests and responses in one place while providing your customers with accountability and responsiveness they deserve.
• HESK : It is PHP Help Desk Software that allows you to set up a Web-based ticket support system for your website quickly and easily.