If you want to speed your page up by 90%:
1) Use nothing but HTML and CSS (ie no javascript, flash) - (99% of sites, and 90% of sites that claim they need it, don't need scripts).
2) Don't use uncompressed images.
3) Use compressed text.
You will also get the benefit of working on nearly every single browser perfectly, even those who use piles of addons like script blockers.
Note - the above can (occasionally) take more effort these days and is often hard to get your boss to agree since they're often impressed when people throw words like Ajax, Rails etc that they have almost zero understanding of.