Seems it's only spreadsheets you can actually embed in a page.
1. With your GoogleDoc spreadsheet open, click the little arrow beside Share in the top R. corner. Select Publish as a web page.
2. Select which sheets to publish. For neat results name the tab for your chosen page simply . . It shows as part of the title when embedded.
3. Click Start publishing.
4. Then, under Get link to published data, select HTML to embed in a page.
5. Select and copy the code in the window.
6. Go to your web page and paste the code into the html. (you might need to enclose it in "code" and "/code" - these are enclosed in pointy brackets in the usual way.
There! When you view your web page the contents of the sheet show in a frame.