A good source to learn the Pali language? I have asked this considering the importance of Pali in Buddhism. 

I want to learn Pali.
 I want to learn it individually on my own. 

Is there any relatively simple way? 

Can anyone suggest me anything?

Any free learning sites will be appreciated.
(Bear in mind, I don't have mastery over the language but I've been swimming in it continuously for the last two years. The following advice is based on this experience.)

There is a whole list of books about learning Pāḷi. Some of them you can find here. I suggest applying the grammar that you learn from them, in Yuttadhammo's Digital Pali Reader (DPR) which will help you learn the vocabulary. DPR has an easy-to-use interface, dictionaries &amp; various helpful tools including one of the grammar books mentioned in the first link.  

These are the resources I use and I complement them with the available translations on ATI, SC &amp; in secondary literature. I also confer this Sanskrit dictionary.

I hope this information will be useful. Good luck.