1Password does work with Firefox 8. - follow the instructions on the 1password website. You may have to open the download with firefox, as it might not come up automatically. Check for it in your downloads and the go to firefox and File and select Open File and choose 1Password.xpi from your downloads.
Check your add-ons under Tools on browser bar. Then look to the far right of your Navigation Bar and you will find the 1password Icon.
If you don't like it's location, the go to View, Toolbars, Customize and move it to the desired location.