Running a help desk within your business can be difficult task, 
SAManage
Thousands of people around the world use SAManage, the leading online IT Service Desk and IT Asset Management tool. SAManage leverages SaaS to empower companies of all sizes with tools that were previously available only to large enterprises, and at a fraction of the cost and complexity.
Spiceworks
Spiceworks is 100% free….really! Always has been, always will be. Thanks to the more than over 200 technology advertisers who sponsor Spiceworks. While the help desk functionality is not the system’s primary focus, it ties in nicely with the rest of the features to produce a fully integrated package. Spiceworks has a tight focus on the smaller companies, and the feature set reflects it.
Remedyforce
Remedyforce is more affordable, easier to setup and use, and designed for your company — no matter the size. It’s everything you need in an IT help desk, without the hassle of hardware.Build and manage your help desk with the experience of thousands of customers and without the pain of programming custom scripts. We built Remedyforce on Force.com, the industry’s leading platform for SaaS applications (trusted by more than 92,000 organizations today). It’s secure, reliable, and backed by our 20+ years as the undisputed ITSM leader.
ServiceDesk Plus
ServiceDesk Plus integrates your help desk requests and assets to help you manage your IT effectively. It helps you implement ITIL best practices and troubleshoot IT service requests faster. ServiceDesk Plus is a highly customizable, easy-to-implement help desk software. More than 10,000 IT managers worldwide use ServiceDesk Plus to manage their IT help desk and assets. ServiceDesk Plus is available in 23 different languages.
Numara’s Footprints Incident and Problem Manager
With Numara® FootPrints® Incident and Problem Manager, you have the power to gain control over the entire end-to-end incident & problem resolution process. More specifically, you can automate, manage, track and tailor your workflow for Incident and Problem Management in a modern, Web 2.0 solution. From the intuitive drag-and-drop Form Designer and customizable Self-service Portal, to the actionable Executive Dashboard, FootPrints Incident and Problem Manager helps you ensure that all incidents and problems are quickly and cost-effectively recorded, managed and resolved.