If I have a lot of functions on startup do they all have to be under one single:
$(document).ready(function() {
or can I have multiple such
Yes you can.
Multiple document ready sections are particularly useful if you have other modules haging off the same page that use it. With the old window.onload=func declaration, every time you specified a function to be called, it replaced the old.
Now all functions specified are queued/stacked (can someone confirm?) regardless of which document ready section they are specified in.