Desi

Word 'desi' evolved from the Sanskrit term 'desha', meaning country. 

Desi nations include 

1. India, 
2. Pakistan, 
3. Bangladesh, 
4. Sri Lanka, 
5. Bhutan, 
6. Burma, 
7. Nepal and the 
8. Maldives.

Organisation

1. http://en.wikipedia.org/wiki/South_Asian_Association_for_Regional_Cooperation
2. https://www.youtube.com/results?search_query=Saarc
3. http://www.slideshare.net/search/slideshow?searchfrom=header&q=saarc

With time its usage shifted more towards referring to 

1. people, 
2. cultures, and 
3. products of a specific region.

There are large Desi populations in the 

1. United Kingdom, 
2. United States, 
3. Canada, 
4. South Africa, 
5. Malaysia, 
6. Mauritius, 
7. Singapore, 
8. United Arab Emirates, 
9. Guyana,
10. Suriname, 
11. Fiji, 
12. Trinidad and 
13. Tobago,
14. Australia, 
15. New Zealand, and the 
16. Middle East among other regions.

Source

http://en.wikipedia.org/wiki/Desi