Basic features like table of contents, footnotes or thesaurus are still missing from Google Docs. Some of the features are already implemented and they're ready to be added to the interface.
(Update: If you have Google Gears, temporarily disable it for Google Docs by removing docs.google.com from the list of allowed sites in Google Gears Settings.)
For example, to generate a table of contents from the headings of a document, just paste this code in the address bar:
You should see a dialog that lets you choose the numbering style.
There's also an option to insert a HTML snippet without editing the HTML code. The dialog can be invoked by pasting in the address bar:
A word processor is more useful if you can easily access a dictionary, an encyclopedia and other sources of information. Select some text from a document and paste the following lines to show information from:
Merriam-Webster's Online Dictionary
Merriam-Webster's Online Thesaurus
Hopefully, these features will soon be added in the interface.