Because of the sorry state of Flash on the Mac (its unnerving ability to bring any computer to its knees), I love Firefox's "Click to Play" extension for Flash. OmniWeb has nothing like this for Flash (although it does for Java). The following is straight from the horse's mouth (OmniGroup) on how to enable Click to Play for Flash in Omniweb:
/* Prevent flash animations from playing until you click on them. */
object[classid$=":D27CDB6E-AE6D-11cf-96B8-444553540000"],
object[codebase*="swflash.cab"],
object[type="application/x-shockwave-flash"],
embed[type="application/x-shockwave-flash"],
embed[src$=".swf"]
{ -moz-binding: url("http://www.floppymoose.com/clickToView.xml#ctv"); }
[robg adds: An earlier hint described another way to add Flash blocking to Camino...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050313224837662