You have the code to vbulletin's md5 javascript added to your template twice, though I don't suppose that would make much difference.
You don't have gzipping enabled which certainly will make a difference, although I'm not sure if the built-in gzip function deals with external javascript files, I suspect it doesn't.
This is well worth reading:
http://developer.yahoo.com/performance/rules.html and is accompanied by a Firefox plugin called Yslow which is very good, although both do require that you know what you're doing to some extent.