MarketWatcher for Mac

From Rampell Software:

MarketWatcher for Macintosh is a powerful program that displays a stock ticker on your screen, with continuously updating, scrolling stock quotes. Besides just showing information, MarketWatcher is interactive, allowing you to find out more about any stock simply by double-clicking it.

MarketWatcher's ticker---or tickers, as you can have more than one---continuously float above all other windows on your computer, so you can see how your stocks are doing, minute by minute. You can even easily check quotes not in the ticker, thanks to MarketWatcher's "custom quote" mechanism. A little button on the ticker allows you to quickly enter a stock symbol and quickly receive information about that stock.

You have full control over the appearance of the ticker and the stocks that appear in it. You can also determine exactly what types of data are displayed in the ticker. Beyond simple stock prices, you can have MarketWatcher display volume, bid/ask quotes, day high/low, etc.