As if the draggable, thumbnail tabs in OmniWeb 5 weren't great enough already (they can be dragged to reorder and also from one browser window to another), here are some more features:
If you double click a tab thumbnail, it will open the page in a new window and close in the old one. Double click the Favicon in the address bar, however, and the page will open in a new window and leave the old incidence of the page where it is.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040822121216791