Disable Google Play Ads in Notification Area?
Airpush! A bloody nuisance they are.

Need to figure out which app did you install recently, that is the culprit. Uninstall it, let the developer know that airpush is disastrous and let them see their downloads drop!

If your handset is rooted, you might try Ad-Away to block those pesky adverts. And its open-source and available on Google Play.