If you dissect the URLs that Google provides when publishing a Doc to the web, you may come across "od6".
"od6" is the worksheet-id of the 'default' sheet within your Google Spreadsheet. That is, the leftmost sheet visible within the interface.
If you have tried publishing all worksheets within the Doc, or any specific worksheet other than the default, as an ATOM or RSS feed, you would have noticed that only the first/default sheet is included in the feed.
To further complicate things, the interface that you use to publish from Google Docs grays-out the drop-down that otherwise would allow you to choose which sheet to publish when ATOM or RSS is selected as your output format. I find this very confusing, don't you?
To address this, you can grab the link that Google provides for your ATOM or RSS feed and edit the "0d6" part to represent the worksheet-id of the worksheet you would like to see. What do you change it to? Well, that's the hairy part. There doesn't seem to be a simple way to find that info.
To determine the worksheet IDs for your spreadsheet, you have to find the data within on of your feeds.
Ask for your worksheet feed by going to:
Review the results and look for the various nodes describing your worksheets. Within each node, you should find the actual worksheet ID for each respective sheet. Worksheet IDs always start with "od" which will usually be followed by a number.
Use the desired worksheet ID in place of "od6" and whalla! All better!