Over the weekend, the famous add URL to Google form was offline.
Google posted a known issue about this saying:
The form to submit URLs to add to our index at http://www.google.com/addurl is currently not available. Our engineers are aware of this issue and working to resolve it.
Keep in mind that Google generally discovers new URLs on its own. Also keep in mind that the use of this form does not affect crawling, indexing, or ranking of URLs that are already indexed.
There are a variety of ways to make sure that Google finds new URLs for your website: we have linked to some of our Help Center articles about this on our FAQ entry about crawling and indexing. Thank you for your patience.
Personally, I don't know if I ever used the add URL form. Maybe I have as a joke or something but never really with intentions of the URL being added. The best way to get a URL added is from a link from a page that gets crawled frequently.
Update: Google has seemed to finally fix this form on October 6, 2010.