This. In addition, you can use "Custom Search Engine" extension on Firefox to create custom search queries on Amazon, YouTube, etc. with keyboard shortcuts. For example, if I want to search for something on Amazon, I type "AA{space}USB Dongle" and it automatically searches the Amazon for "USB Dongle". The neat thing is that I customized the search URL so that "AA" also filters the results (shows only +4-star products, New, and Prime).

I've done similar thing with YouTube where I type "YY{space}" from anywhere and end up searching on YouTube.