JPigford: have you tried wiping your drive clean and installing fresh? Also, if so, you may want to try one more time, checking the stability of the system before installing anything else. Try using Spotlight (once done indexing your hard drive) to search in the bodies of emails as well as check the other problems you were having.
Then, install new applications you need one-by-one, checking stability after each install. I have a feeling that something is corrupt on your system, and Tiger isn't properly configured because you're having WAY too many problems to chalk it up to "Tiger bugs." It sounds like the install didn't go well or that something just isn't working right that should be due to corruption somewhere.
Also, I remember seeing a thread here that alluded to dual-processor machines being unstable with certain areas of Tiger -- much more than single processor machines. I don't think that's the underlying problem, but you never know.