Some interesting comments from Google employee Matt Cuts about the google index update time. Essentially the days of huge "Google updates", or "Google dances" are over by the sound of it. I guess they've expanded so much that "real time" (or close enough to) indexing is more than possible.

As a side note, I'm going to mention webmaster tools again, from there you can check when your site was crawled last, and more importantly - you can actually add your sites RSS feed directly into the google sitemaps console. Periodically (usually very quickly) Google will download your feed and any new content you have.