This is old news in some ways, but the update is still happening so I consider it fair game. You may have experienced a drop in both PageRank and keyword rankings. This seems to be a bigger update than usual.
Google’s new system, introduced in the last couple of years, was supposedly to be one of ‘Constant Updating’. The idea being that we wouldn’t see the sudden catastrophic drops across the board that the search word experienced before. Businesses who have been around for a few years online can tell you stories of Google updates that came close to putting them out of business.
The lesson there might be ‘Expand your marketing to create other sources of business’ instead of ‘Google Sucks…sometimes’, but I don’t want to preach. The current concern is that this update is reminiscent of those old days, bringing mass upheavals that have affected a lot of industries.
What should you do if your search rankings dropped? Keep working on your SEO, pushing ahead. Look for anything you might have done that created problems (like selling links on your site). Don’t Panic. If you’re doing the right thing(s) you’ll probably rise back up in time. And start looking for other ways of generating business. Depending on one search engine, especially the occasionally volatile Google, puts you at their mercy for your livelihood. Think about that and plan accordingly.