But I use Camino. Extensions are not widely supported in Camino for various reasons, but some can work. I found some threads on Mozillazine and the MacOSXHints forums on how to install Flashblock in Camino. But all of the discussions instructions require either a Firefox install or Mozilla install. So I figured out how to do it without needing Firefox or Mozilla. As with anything of this nature, you are at your own risk -- and you might want to backup your Camino profile before starting.
First, you need to visit the Flashblock site and go to the "Installation" section. Control-click on the Firefox install link, and chose 'Save the target as...' from the pop-up. Either rename the file at this step, or after you download it -- but it needs to be renamed from flashblock.xpi to flashblock.zip. This way, you can unzip it normally with the Finder. Go ahead and unzip the file.
In the unzipped folder, you should find another folder called 'chrome,' and in there is the flashblock.jar file. This is what you need. Copy that .jar file to your user's Library -> Application Support -> Camino -> chrome folder. Now you need to make changes to two of the other files in that same Camino chrome folder. Make sure that Camino is not running at this point. You might also want to make backups of these files before editing (for good measure). The first file is userContent.css. Using the text editor of your choice, add the following:
/*flashblock*/
@import url(chrome://flashblock/content/flashblock.css);
/*end flashblock*/
The next file is chrome.rdf. Just before the final you should add the following:
<RDF:Description RDF:about="urn:mozilla:package:flashblock"
c:baseURL="jar:file:///Users/yourUsername/Library/Application%20Support/
Camino/chrome/flashblock.jar!/content/flashblock/"
c:locType="profile"
c:displayName="Flashblock"
c:author="The Flashblock team"
c:authorURL="http://flashblock.mozdev.org/"
c:name="flashblock"
c:extension="true"
c:description="Replaces Flash objects with a button you can click to view them." />
VERY IMPORTANT NOTE: The c:baseURL line has been split into two for a narrower display. Make this one long line with no added spaces, and make sure to change the path to match where you put the .jar file earlier (probably just change the yourUsername part to match your username). Make sure that if you have any spaces in the path that they are "converted" to HTML (such as in Application%20Support) by using the %20 space equivalent.
Save the files, and open Camino. Now, navigate to a site that has Flash, like Homestarrunner, and you should see a neat icon instead of the actual Flash. Click on it and it should play! Your mileage may vary. This might only work with English-US localizations. There are other localizations in the chrome.rdf file that Flashblock installs in Mozilla and Firefox, but I didn't pull them across in my implementation.

