Auto Copy is a free Firefox add-on that, as the name suggests, automatically copies the text you select inside your browser, with no additional key combination.
If you have to do a hark work of copying and pasting between two web pages, or you are just to lazy to press any key, Auto Copy is definitely the tool you are looking for.
Although it is a really simple extension, it has plenty of options you can set as you like: you can deselect the text after it has been copied, enable copy in text boxes and plain text areas, integrate a status bar button on the bottom of Firefox and more…
The function I liked the most is “Autocopy Context Menu”.
After you select a text, a context menu will appear automatically, allowing you to decide what to do with the text that has been copied: you can undo the copy, browse inside previous copied text, automatically paste the text inside the search or the location bar and also open the text in a new window.
Auto Copy is free to download and use.