The answer is Yes, you can use two displays with a Raspberry Pi, but you will need to buy some other components depending on how you want to use those displays. You'll need an adapter with a DisplayLink chip or a VGA666 Adapter to use it as a true secondary monitor.
The most common reason people want to use two displays with raspberry pie is to have an extended desktop environment, as you see on larger, more expensive computers.This is doable with an inexpensive USB to VGA Displaylink adapter and a bit of knowledge about reconfiguring the kernel and X Windows configuration of your operating system.
A secondary display
You can also use the second display to run applications that drive the GPU directly like media players. This is useful for an application that might use a small LCD as a controller but display video on another screen, such as a programmable sign or kiosk. It's also a lot simpler to set up because it doesn't need a new kernel.
A Raspberry Pi is a great little device for a lot of things — including a miniature desktop PC — but it lacks the power and ports to do everything. Sometimes, you just have to go bigger. Just make sure you know what you're doing first.