A WebmasterWorld member wants to know if you're alerted if your website has any penalties.
According to tedster, you might get it in your Google Webmaster Central account, provided your site is registered with Google. (If it isn't, now's a good time to get it set up! What are you waiting for?)
Some webmasters get an email or a notice in their webmaster tools account, especially when the penalty is for something that might even be accidental.
This is a sure-shot way to keep your relationship with Google healthy and happy.
Ted also offers other words of wisdom. Don't think that your site is being penalized in the event of a drop or rankings (or even PageRank! Thanks, Matt Cutts, for the clarification).
Also, appreciate that every drop in ranking is not a true penalty, in Google's terms. Some webmasters are rather casual about using the word penalty for almost any drop in ranking, when in many cases, it could just be a change in the algorithm.
So if your site drops for certain search phrases, just keep monitoring it daily. It may not be a penalty after all.
Forum discussion continues at WebmasterWorld.