Ticketing Tools

Open Source Ticketing Tool
SpiceWorks:
osTicket
Freshdesk

Ticketing Tools:
PinkVERIFY 2011 Toolsets
PinkVERIFY 3.1 Toolsets
PinkVERIFY 3.0 Toolsets
BMC Remedy ITSM Tool
ServiceNow
HP Service Anywhere
Zendesk
ServiceDesk Plus from ManageEngine
assyst Service Management Software
assystSaaS
Marval
Cherwell Service Level Management Software
Hornbill
Service Desk Tools
MyServiceDesk
Helpdesk Report
Helpdesk and IT Software List
EasyVista
HarePoint HelpDesk for SharePoint
HarePoint HelpDesk for SharePoint Editions comparison and roadmap
Help Desk Premier

Link to the list of 300+ ITIL tools
Free HelpDesk tools for ITIL / ITSM
ITSM / ITIL / Help Desk Tools
IT Service Management Tools from Kloudax
The Forrester SaaS ITSM Tool Market Overview: Who Is Where With What
Source:Wiki
Comparision of help desk issue tracking software
Comparision of issue-tracking systems
Magic Quadrant for IT Service Support Management Tools

Want to know the difference between Help Desk, Asset Management, ITIL Ready

How to choose a perfect Service Desk/ITSM tool in 5 days?

http://www.itsmcommunity.org/Resources/tools/
Staffing Calculation Tool For Service Desks
OGC Self Assessment Tool For ITIL Service Delivery
OGC Self Assessment Tool For ITIL Service Support
ITSM Metrics Modeling Tool
DICE Model — ITIL Project Success Prediction Tool