I use firebug in firefox to debug javascript in the console tab... there are equivalents for most browsers. Chrome has a debugger built in.
Once a page hits a javascript error, it will sometimes stop trying to run scripts lower on the page... So I refresh the page with console open and see if any errors pop up.
The error that popped up was something like "bigSlide is not defined".. so I looked at your page to see where it was referenced and I saw you had a script referring to bigslide, and had the bigslide.js file before it, so it should be defined. But I also saw that bigslide was based on Jquery and that your jquery .js files were below.
It is a pretty common error to not have jquery files in the right place, or to have more than one set on the page, so it is something I'm used to looking for... so I tried moving the jquery files up on the page and sure enough it worked.