Take your new content and quite literally shove it up Google's ..... If you have a webmaster account with google, update your Google (XML) sitemap every 4-5 days and re-submit it. The Bots love this and it really does help long term with SERPS. Add in more links each month (about 30 per month) and don't expect to be back at the top of the SERPS for your particular keywords for at least 6 months!