From 1995 through 2001, Tonya and I participated in a stock investment club with a number of our Mac-using friends. It was a valuable learning experience, and the club did fairly well, though it was difficult to do badly in the stock market during some of those years. We worked mostly within the advice promulgated by the National Association of Investors Corporation (NAIC), and although that system wasn't terribly data-intensive, we still found it difficult to enter data for stocks we were investigating and to keep up-to-date with stocks in our portfolio. Some online services offered downloadable information for a fee, but either the fees were too high or there was some other problem with the service, such as working only in Windows. Tonya and I bowed out of the investment club when we left Seattle, and without the structure and positive peer pressure of a monthly meeting to make time in our busy schedules, we've essentially stopped investing in individual stocks.
I can't say when or if we'll pick up investing again, but there's now a Macintosh application that looks as though it would provide the kind of data we wanted in a flexible manner. WillStein Software's Stock WatchTower downloads a vast amount of data covering thousands of stocks from a variety of freely accessible Web sites on its first launch (about 150 MB), and updates that data with much-faster but still significant (about an hour over a broadband Internet connection) downloads on every subsequent launch. Using that data, you can then filter and sort just the stocks whose data matches criteria you set: P/E ratios within a certain range, current annual earnings over a certain amount, prices nearing 52-week highs, and so on. Stock WatchTower can then graph each stock's data so you can more easily identify buy points, or, for stocks that you already own, prices at which you want to sell. You can create Watch Lists, which are manually generated lists of stocks much like playlists in iTunes, and WatchTowers, which are automatically generated lists akin to smart playlists.