Sanskrit

Sanskrit Palm-Leaf Manuscript: Image Source
Sanskrit is the source language of Yoga and Ayurveda.  It comes from ancient India and is the ancestor of the Indo-European language family.

Referred to as "perfected" or "refined", Sanskrit is highly respected as a language of ritual, science, technology, and mathematics.

It is written in a script called Devanagari, the same script as modern Hindi.

Despite a complex grammar and vast vocabulary, Sanskrit is a systematic and phonetic language, which makes learning it easier than you might think!

Here are some resources for beginners:

Sanskrit Pronunciation Guide by Tilak Pyle

Sanskrit Dictionary

Glossary of 108 Yoga terms

Khan Academy: Sanskrit Connections to English

List of English words of Sanskrit origin

Basic tips for learning Sanskrit.

Manorama's YouTube Channel, Sanskrit Studies and Luminous Soul

I highly recommend the following if you wish to explore Sanskrit in depth:

Devanagari Script Tutor

Cambridge Introduction to Sanskrit

South Asian Studies Department, University of Alberta

Shiksha

Sanskrit is currently experiencing a Renaissance of sorts; an effort to revive it as a colloquial, or spoken language:  Samskrita Bharati

Patrick McCartney spent a month in India where the village of Jhiri is attempting to do just that.  He documented his visit in a series of short films:  Imagining Sanskrit Land

Lastly, if you find yourself overwhelmed by the effort of language learning and the quest for worldly attainments in general, try listening to the words of Adi Shankaracharya in his famous work Bhaja Govindam

bhajagovindam bhajagovindam govindam bhajamuudhamate 

sampraapte sannihite kaale nahi nahi rakshati dukrijnkarane

"Sing Govinda[Sing the lord's name], Sing Govinda's name, Sing Govinda's name. 
Oh, fool! Rules of Grammar will not save you at the time of your death."