Is it true that there are 5 principal types of meditations? According to some there are 5 principal types of meditations:


Metta-Bhavana 
Karuna-Bhavana
Mudita Bhavana
Asubha Bhavana 
Upekka Bhavana


I couldn't find any link which could support the above mentioned meditation theory.

So my questions are:

Is it true that there are 5 principal types of Meditations?

Can anyone provide me the original links where Buddha lays down the above mentioned 5 types of meditation?
Yes and no: i.e., "Yes, there are 5"; and, "No, there are more than 5".

4 of the ones you listed are to bring into being what are known as the 4 "Brahma-viharas" (of which, metta-bhavana may be the most famous).

I'm not sure that types of meditation are detailed in the suttas (some are). Various types may be detailed in more detail in the 5th century Path of Purification (Visuddhimagga). If I were looking for references to them in the suttas I think I'd start search by searching in accesstoinsight.org (searching for "Brahma-viharas" and/or "metta" and so on).

The fifth one, Asubha, is meant as an antidote to lust: and so, for example, it's contemplation of the foulness of the body (e.g. the Asubha Sutta, and one of the meditation types mentioned in the Satipatthana Sutta).

Other principal types include meditation intended for insight, concentration, mindfulness, tranquility, detachment. They're named things like "Vipassana", and "Anapanasati" (Anapanasati Sutta)

Samana Johann linked to a reference which lists "40 types" (in reply to another question of yours).

The ones I've listed are from Theravada (Mahayana may have others).