If you have fresh content that isn't being indexed as fast as it once was this may be the reason - http://searchengineland.com/is-google-broken-sites-big-small-seeing-indexing-problems-53701
Alternative search engines you should be paying attention to - http://searchenginewatch.com/3641484
Tweaking your tags to drive clicks - http://searchenginewatch.com/3641483
Some good info from SES Chicago - http://www.clickz.com/clickz/column/1810090/horses-mouth
Have a wonderful Tuesday.