So far the best stock watchlist I came across is from Bloomberg. Registering is free and very easy (especially with facebook connect). You can quickly add stocks to the list, even if you don't remember the ticker symbol, thanks to the 'auto complete' feature.
|Example of Bloomberg's stock watchlist|
There are also others like Yahoo, Google and MSN Money where you can create a watchlist, but I found them to be a little cluttered, though they do have an option where you can also see the news about the company on the list. However, 'news' isn't always a good thing (since it's usually delayed).
Checking your stock list frequently may help you become a better stock trader. You might discover certain price patterns, or be reminded of stocks (opportunities) that you may have otherwise forgotten. You can add stocks to the list that you don't really want in your portfolio right this second, but maybe at a later time. Of course the advantage of an online watchlist is of course that you can check it online anywhere you are. You can also put stocks on the list that you would've bought if it were an actual portfolio (like a stock trading simulator), Bloomberg's online stock trading watchlist is ideal for that because of its 'Holdings' feature, which allows you to enter a price for which you would've bought or sold a stock.
Go create your own watchlist on Bloomberg here.