Posting about Thickbox reminded me of this lightbox jQuery plugin, which has become my current fav for putting together quick galleries (like for flickr feeds and such). I'm also a sucker for the nice design at the site. And, as an extra bonus, picking through the source of this page is how I originally found the idTabs plugin (way back when this plugin was originally released), which has become one of my most frequently used plugins.

Anway, back to the point, here's the jQuery lightbox plugin:

http://leandrovieira.com/projects/jquery/lightbox/

I've found it to be nicely reliable across browsers, and it "feels" lightweight, requiring minimal mucking around the in the CSS to get it working and to style it (though I've gotta say I haven't had much need to actually mod it's styling). FYI, we almost always use a CSS reset file (usually the YUI one, but sometimes just a plain old * reset for setting padding and margins to 0) and this has played very nicely with that.