I have a Pages (iWork '08) document I'd like to work on on my laptop, but my laptop doesn't have iWork. When I try to open the document, it turns out to actually be a folder with several things inside, but everything seems to be meta information. Is there a specific file in there I can open in Textedit and work on, and if so, which one?
iWork '08 saves it's files as bundles which will appear as a folder with files within it. iWork '09 unless you turn on "Save files as packages" in the preferences saves it as a flat file now.
index.xml.gz file is a gzip'd version of the text and formatting rules (in xml) of the file). It's possible to unzip this file, make an edit and then rezip it back up but I would advise against it as the work unzipping, rezipping and handling the xml is not really worth the hassle.
Without access to iWork there isn't much you can do - you could export from Pages as an .rtf as TextEdit will be able to edit and work with those as well as Microsoft Word documents.
as you already have noticed, the iWorks file is a archive file containing multiple other files, your images etc. the text part of this file uses XML for formatting.
more details can be read here: http://ctrambler.wordpress.com/2007/08/21/iworks-xml-format-vs-odf-vs-ooxml-preliminary-thoughts/
as a concequence, you're unable to open it Textedit, however, there are two different ways you can go from here
You might want to try opening it with OpenOffice.org Writer, which should support an iwork-pages document.
If your document only contains test without any type of markup, you might want to save it as a plain text document instead of an iwork pages document note that this will remove all formatting from your file thisĺl allow you to open the text document with Textedit