The The Qt Mailing Lists provide a developer community and searchable archives. Searching on a class you are trying to use, or an error message you do not understand, can often give you useful results.

Qt Developer Network has technical articles and tutorials about Qt.

QtCentre is a Web-based online community site devoted to C++ programming using Qt. It puts you in touch with people all over the planet who use Qt and help one another out. There are numerous forums, projects, and FAQ. This site is constantly monitored by key Qt developers who often participate in forum discussions, make announcements, and give useful advice.

ics.com is a training and consulting partner of Nokia, providing on-site consulting and consulting services for people with need of Qt expertise. This is a shameless plug, because one of the authors is employed there.

If you encounter a seemingly intractable error with an error message that is not too long, try pasting it into Google.