You can also give
http://www.samspade.org/ a look, that's what I use a lot for reverse lookups here at work.
Now, if the guy who spoofed it was really up to snuff, it's probably a spoofed source IP also, but if he just connected to an SMTP server and did it there then it will list his true IP address, or at least the last machine he was on (if he made multiple connections to get there). I wouldn't put too much stock on that IP address, as I can telnet to a shell acount in CA, then telnet to an smtp server and it will appear that the email came from CA, when I am in IL.
But you can use quite a few tools to do a WHO IS and lookup who owns that address block.