I just replaced the timing chain, crank and camshaft gears, and chain tensioner. After putting everything back together, my car squeals, but its a serpentine system. Its a lot louder at idle than when the RPMs rise. I've been driving it around for a little bit and that's the only problem I've run into, no leaks or any problem with timing. Any idea what it is?

 

Did you touch the top end of the engine at all.. I know if you fuel rail is the slightest bit loose it will make a horrible squealing noise. If so just push down on it a few times and make sure its in. then tighted it back down. It happend to me a few times. Well I had most of the engine torn down. not just the timing cover

just an idea.

And serp systems can squeal also.. Maybe you did't aliagn the pullys right

 

Pull the serp belt off and run the engine to see if the sound goes away.

 

I never knew that serpentine belts could squeal, but I found that they do today when I tried an old belt I had from awhile back. The squealing went away w/ an older, more worn belt. Go figure... at least she doesn't squeal anymore.

 

During replacing all the parts perhaps you got some grease on the belt.
That may be your cause of squeal, too.
You did replace tensioner & also add a balancer repair sleeve?