SEO Update

# Dig your internal traffic analytics for traffic drops or bad trends;

# Perform [site:yoursite.com] search in Google to see if Google reports same number of indexed URLs;

# Check if Google Webmaster Tools report any problems;

# Take a look if Google toolbar PR has changed (graybar PR might be a signal of penalty);

# Check your site ranking for a “domain-name” search (without the TLD).

via 10 Ways to Diagnose a Google Penalty.