StockTicker is a helpful Firefox extension that displays a ticker for defined stock symbols. It is pretty straight forward. After installing the extension, it will add a ticker below the Bookmarks toolbar. To add symbols, right click and select Add/Edit… If you already know the symbol just enter it, otherwise, press Symbol Lookup to be directed to Yahoo! Finance site and search for the symbol by company name. Then you add a description or long name, the number of share you own and the price you bought them for if applicable for portfolio valuation. Then you can specify what information you want to see for that symbol or whether you prefer the default view.

Options to display the ticker in the status bar (then hide the StockTicker toolbar to save screen estate), specify a different stock information provider (like Google Finance), ticker speed and refresh rate make StockTicker a complete though compact extension for monitoring your portfolio.