How can I fix my 2000 Nissan Frontier suspension noise problem?

I have a U.S. spec 2000 Nissan Frontier 2-wheel drive (4-cyl) model with 131K miles on it and I'm hearing a squawking/squeaking sound coming from the left front side of the truck every time I hit a small bump or turn the steering wheel slightly from side to side. The noise is especially prominent when it's cold outside. The Monroe shocks are only 4 months old and the noise was there before replacement (but is more noticeable now). Is this a bushing problem? Are their grease fittings on the front end or steering control? Any ideas on how to diagnose and correct the problem would be appreciated.