Google Webmaster Tools has a page for submitting a url to Google. Google will queue then try to re-index the requested page, but it doesn't guarantee that it will do so. Here's the extracted disclaimer:
Google adds new sites to our index, and updates existing ones, every time we crawl the web. If you have a new URL, tell us about it here. We don't add all submitted URLs to our index, and we can't make predictions or guarantees about when or if submitted URLs will appear in our index.
I guess it means they will try their best! It's better than nothing :)
The full url of the tool is https://www.google.com/webmasters/tools/submit-url