Help Connection.NET (by Expinion.net)
HelpConnection.NET will help your company offer superior customer support.
If clients don't find their answers in your knowledge base, they can submit tickets via online forms or incoming email (or your agents can enter the info for them if they call in). The issue will be logged in the system, and the appropriate agents will be notified by email (and on their online home page).
Help desk tickets can be captured from emails, online forms or twitter tweets! Reply via email, online form or twitter too.
Other Features: Customizable fields, advanced search functions, nested categories, no limit to number of clients / issues, canned answers (drafts), custom agent security levels, assets manager, tasks/scheduling, etc. Agents and customers can be allowed to upload files, and emails can be converted to tickets. Be sure to customize the emails for your own flavor, change some of the many available settings, and add your own site headers and footers. APIs included.