Hi,
I’m not an expert on this topic, but I see some things right away that can easily slow your site down.
It looks like you’re pulling in live feeds directly from Facebook. Anytime you rely on content from another site, that can slow you down. Same with Twitter or other “feeds”. For instance, even if your site is very fast, if Facebook slows down at all, your pages will load slowly, I think. Many people are surprised by this, and if they get a feed from a site that’s often slow, their own site’s performance will be poor, no matter how good their hosting is.
That moving Tag Cloud is cute, but I would bet that it slows your site down, too.
Lastly, I ran your site through HTML validation, and there are a lot of errors, way too many to just say “fix this…” Mostly non-XHTML stuff in an XHTML template. It may or many not slow you down.
Good luck, Dave