Thank you for your message. I understand that some Gadget have inappropriate content.
There is a tool available to you, the Feed Server Client Tool (FSCT)
which will let you control which gadget appear in the Google Sites
gadget directory for your domain. You can visit: http://edutraining.googleapps.com/Training-Home/module-5-sites/chapter-8 for detailed instructions on that tool.
You can also take a look at the topic regarding 'Block and allow certain
gadgets in Sites' which will also allow you to block all the unwanted
Gadgets that are available.
I am able to provide you with this information, however cannot offer any
further assistance as this is not a supported feature of Google Apps.
If you have any questions regarding your account, please do not hesitate
to communicate with me and I will gladly assist you further.