A Contact (or Comment) form for Google Sites
Notice that under step 6 you will be notified that someone has submitted your form, and then you have to open up the spreadsheet to see what they entered.
If you want to use this as a comment form where the comments are posted on your site click Share while editing the spreadsheet and select to share it to the public and to automatically re-publish when changed and click Publish as a web page. Insert the spreadsheet itself as shown below. Look at Steegle's instructions here or Raveen's instructions here for detailed information.
Stephen Hind (Steegle) has just posted information that Google now provides scripts you can add to spreadsheets, so now when a Google Sites visitor uses your Google Spreadsheet Form you can have the response e-mailed to you, rather than having to go to the spreadsheet. His instructions are here.
If you want your comments sorted (last comment at the top) be sure to read Steegle's instructions.
Your post will appear here after a few minutes. Refresh the page to see it.