My ISP provides dynamic IP whenever I am connecting to the network. How can I find my current IP address of my Ubuntu 12.04 Desktop system?
Your ISP will issue you an external dynamic IP for your router. This isn't the IP your desktop is using, it'll get that from the router via DHCP unless you've manually configured static, which I don't think you will have. You can run IFConfig from the console and it should list all available interfaces and IP addresses attached to those interfaces. The name of the interface will differ depending if you are on a wired or wireless connection, but is most likely labeled 'eth0'
If you want to find your external IP, Google 'Whats my IP' and Google will tell you.