WARNING! This website is no longer actively maintained. It is an archive of 2 years work by Doug Belshaw who now blogs at dougbelshaw.com...
Google have integrated the fairly-recently-purchased Writely with Google Spreadsheets over at Google Docs. It’s not tightly integrated (yet) but I like the familiar crisp, clean interface and the collaboration aspects. You can’t embed a spreadsheet in a document at the moment, but apparently this feature is coming soon. What you can do, however, is the following: save files in Word, OpenOffice, HTML and PDF formats; invite people to collaborate on a document; perform word counts; find and replace words (still experimental); publish documents quickly and easily to the Internet; publish to your blog directly; view revisions made to a document; and more that I haven’t had a chance to discover yet. Isn’t Google great? More about Google Docs by Google and Techcrunch. 
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I’ve been using Writely for some time now - and I have tested publishing to a blog with it (a Word Press one, not tested the Elgg one that I’ve also got).
What I’m looking forward too though is when the upper left corner of a logged in page of google shows the same set of links …
- when I go to the Docs page:
- on a Gmail page
- on my Google Personal page.
Incidentally, if you have a Google personal page, have you noticed that it you use the .co.uk URL you don’t get the option for tabs on the page, but if you go to the .com URL you can have tabs to organise things. Natch, if you’ve sorted out on .com, and then use .co.uk it puts them all back on the same page. At least you don’t loose them!