Redirecting static file to nginx from apache

It will be faster to just have Apache serve the file than to offload it to another webserver, but you might want to elaborate on the actual "various reasons" you can't get nginx to work in front of Apache.

Getting nginx or lighttpd to serve up all your static files and proxy dynamic requests to Apache/FastCGI is an easy way to really lighten the load on Apache and your server. What's your setup? A bit more info about what, exactly, you're trying to do might elicit greater responses.