When you are signed into the site (as you were to post this question), click on 'My Photosynths' at the top of the page. When you see the list of your synths, you should see a small 'x' in the top right corner of each synth's or pano's 'Synth Card'.
When you click the 'x', the synth or pano will be permanently deleted.
Right now I see that your profile has no public synths or panos, so I assume that either you have already figured this out, or you have only created unlisted synths so far.
Also... just a small note: The 'Announcements' forum is meant for the Photosynth team to make announcements to us, not for us to make announcements of our own. It's no big deal, but if you have more questions, perhaps you might ask them in the Lounge or the Advice forums.
I hope this helps!
Your fellow photosynther,