JStock is an elegant little utility that once installed gives you updated (live) information about current stock market. It fetch these data from 25 different stock markets all around the world such as Australia, Hong Kong, India, Italy, etc. For the sake of integrity/quality, the public data is gathered from Yahoo finance.
Not just one, but you can set multiple watch lists with it as well. You can easily create a database of your transactions (including small notes, etc) and lets you calculate your net growth + buy and sell records too. Since you can't just stare at your Laptop/PC screen all the time... (well some do it ;-) ) once setup, it can automatically send you important "alerts" via SMS, E-Mail or using the standard desktop notifications as well.
Although these are very few of its main features to mention. If you want to install it in GNU/Linux then first make sure you've already installed Java.
If so, then please download the package from here and exactract the content. Then double click the file called "JStock.sh" and follow the instructions on your screen. For MS windows, Mac OSX, Solaris users, you can get JStock installer from here.