I would check the quality of the content (human readability and usefulness) and then, so long as all is good with the on-page SEO as you say it is, I would ensure I have social bookmarking buttons in prominant places, and open accounts on the major social sites (twitter, Facebook etc) and try to make it as easy as possible for folks to bookmark the content.

I would spend just 30mins initially following a few people that appear interested in the industry.

Then:

If it is an ecommerce site, take a feed from the mysql database, and modify it for Google Base (quick once you know how). If the site used an open source shopping cart/CMS, then there is likely a plugin/modification for free or cheap to do this instead of going into the database directly, as so this could be automated.

Also if it is an ecommerce store, I would ensure the h1's are showing correctly on every product page, and that there is GREAT (and I mean GREAT) navigation throughout the site (in fact, this goes for most sites, not just Ecommerce ones).

If it is a site that's based on a blogging platform (wordpress etc) then I would check the RSS feeds, and submit them to decent RSS sites, to aid indexing.

Follow that by looking for some guest post availability, write and submit a decent press release about the new site launch (be sure to submit to Google News sources!) and finish off by doing an hours extra work over a coffee, drawing up some flow diagrams of the next steps. Part of this final step would be working out how much time I could realistically spend each week or month on tasks for this website.

Phew, that's a fair bit for 8 hrs, but it is realistic if you get your head down, and keep the coffee flowing.

I hope this helps, but I bet some guys and gals will disagree with what I have said! Still, each to their own!