Outside of littering the site with social iframes, that is.
Plugs welcomed! :)
EDIT: Suggested rewording of the question - how to build feature rich dynamic services on low cost vps machines?
Think of it like this, I shouldn't have to immediately pop up a dialog box, navigate to a different page, or stop what I'm doing to share something. I certainly shouldn't have to copy and paste a URL into a shortner and then into something like Twitter.
Apart from that, something like Disqus's comment recommendation/voting system, but applied to divs on the page. Instantly apply some javascript magic to static content.
There are a few other ideas along those lines, and it suprises me daily that there aren't more javascripts that can be dropped into a static page and enhance the semantic content of the page.
I guess something like Parse would help here too, a lot of time building an independent script for any of these is spent on the backend, which could be abstracted away with a backend service like Parse.