One of the advantages to having web-based documents is that you can open them from any desktop in multiple browsers.
I use Google Apps for my online office suite, but find that Zoho is a strong competitor for many reasons. One thing I like about Zoho is that they publish a URL that allows you to open a 'scratch' worksheet. Zoho does not require an account for this spreadsheet. If you have a Zoho account, you have the option of saving it when done. Otherwise, you can quickly do spreadsheet calculations, export it, save it, or close it when you are done.
But what about Google Apps? Do they publish a similar URL? It turns out they do, but it is hidden. After trial and error (and watching my browser carefully), I was able to come up with the URL for a new Google Apps spreadsheet. (Note: This URL requires a Google Apps account - which is free.)
The URL is as follows:
http://spreadsheets.google.com/a/[Google Apps Url]/ccc?new&hl=en
Where [Google Apps URL] is the URL to your Google Apps. Just post it on your iGoogle bookmarks widget and you can start launching new spreadsheets right from your homepage.