With JustAnswer, you can ask professional mechanics about your car questions. You pay only a very small fee if you think the mechanic answered your question to your satisfaction.
AutoMD is the comprehensive online automotive repair resource designed to empower car owners with the best way to repair their vehicles.
Carsurvey has lots of owner-written reviews of most vehicles, both positive & negative, organized by vehicle make.
ConsumerAffairs.com tracks complaints of all types, including vehicle & dealership complaints.
Edmunds is one of the best general vehicle information sites. Lots of ads, but they do have decent information on both new & used vehicles.
Epinions is definitely a corporate-run site, but does have some useful reviews (positive & negative) if you can get past all the ads.
OBD-Codes.com is a great resource for help on OBD-II trouble codes. Site also has an active forum section for assistance with tricky issues or questions about OBD codes.
The Open Directory Project
The Open Directory Project has a comprehensive of vehicle complaint sites, both general vehicle complaint sites like CarComplaints.com, as well as complaint websites about specific vehicles & dealerships.
Ask a question about how to fix a common problem, look for a mechanic or research more complaints about your car -- Check out these other car problem resources: