Cached, PHP generated Thumbnails load slowly

First, using those multiple domains requires several DNS lookups. You'd be better off combining many of those images into a sprite instead of spreading the requests.

Second, when I load your page, I see most of the blocking (~1.25s) on all.js. I see that begins with (an old version of) jQuery. You should reference that from the Google CDN, to not only decrease load time, but potentially avoid an HTTP request for it entirely.

Specifically, the most current jQuery and jQuery UI libraries can be referenced at these URLs (see this post if you're interested why I omitted the http:):

//ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js

//ajax.googleapis.com/ajax/libs/jqueryui/1.8.9/jquery-ui.min.js

If you're using one of the default jQuery UI themes, you can also pull its CSS and images off the Google CDN.

With the jQuery hosting optimized, you should also combine awmlib2.js and tooltiplib.js into a single file.

If you address those things, you should see a significant improvement.

I had a similar problem a few days ago & i found head.js. It's a Javascript Plugin which allows you to load all JS files paralell. Hope that helps.