I know that we've posted about .htaccess files and friendly error pages before, but after some questions from my spouse, I decided to write up something more along the lines of a package of scripts. It contains a bit of optional logging, if you want to keep an eye on the details of your errors, but that can be turned off if you want.
My full entry (although not much longer than this) about the package is available here; you can also download the zip file and just work from the README I've included.