An interesting Article on Indian Communities / Caste in India :-

Madhava Community

The Madhavas are Vaishnava Brahmins. The affiliations of the Madhwa philosophy extended in the form of temples and monasteries from Udupi in the South India to Dwaraka in West India to Gaya in the East India to Badrinath in the North India.

The traditional occupation of Madhwa Brahmins is priesthood, but they also engaged in occupations such as agriculture and the business.

Madhwa Brahmins are pure vegetarian. Most Madhavas are erudite. They rarely intermarry with other sects. Madhava men can be recognised by their distinctive Vaishnava caste marks, such as, the 'akshata' (round dark mark) and the 'angara' (a vertical central charcoal-black line drawn on the forehead), the additional sandal paste caste marks on the arms, chest and abdomen representing the sankha (conch), padma (lotus) and the like. At home the women and girls worship the tulsi plant daily. But in custom, tradition and dress the Madhavas can hardly be distinguished from Maharashtra Brahmins. The mother tongue of many Madhava families of Madras and Tanjavur is Marathi.

Maheshwari Community   

Maheshwari, also spelled Maheshvari, is a Hindu caste of India, is now in Rajasthan.

The meaning of the word "Maheshwari" is "great worshipper". The Banias of Rajasthan are often known as Marwaris, and are also known as Mahajans. There is a community of Meghwar people in the state of Gujarat who also sometimes use the Maheshwari name but these people are Dalits, unrelated to the Banias, and adopt the name to signify their devotion to the god Shiv.

Their traditional occupation is that of commerce. They are predominantly a business and mercantile community.

The chief language spoken by them is Marwari or Rajasthani . Maheshwari is famous for their Cotton Silk Dress Material 

Mleccha

Mlecchais an abusive term given to the people who did not conform to the ethical and religious rule of the Indo-Aryan society. They were deprived of the usages and the study of the Vedas and referred to those of an incomprehensible speech, foreign or barbarous invaders as contra-distinguished from Aryan Vedic tribes.

Mleccha people of foreign extraction in ancient India. Mlechchhas were found in north-western India, and there is reason to believe that the people known in Akkadian as Mlakkha were the original mlechchhas. As a mlechchha, any foreigner stood completely outside the caste system and the ritual ambience. Thus, historically, contact with them was viewed by the caste Hindu as polluting.

It is believed that Mleccha is related to Meluhha, the name of a trading partner of Bronze Age. In the later Vedic manuscript, Shatapatha Brahmana mentioned the name Mleccha. Baudhayana, the law maker describes a Mleccha as a person who eats meat or indulges in self-opposing declarations or is devoid of virtue and purity of conduct and also who do not speak the sacred language Sanskrit.

Mohyal Community

Mohyal Community is a Punjabi speaking community living mostly in the states of Punjab, Haryana, Delhi and Uttar Pradesh. 

Mohyal community people were primarily Brahmins who left their priestly duties to serve as warriors, piritual healers and preachers of different sects of Hinduism. As a part of this transformation, many Punjabi Hindus, including the Mohyals, revered and followed Guru Nanak. This devotion towards Nanak's mat (teachings/wisdom) led them to follow Nanak's successors and then assist in the creation of the Sikh ethos. Moreover, as the latter Gurus became martial, this community was a natural home for the warrior-class of Punjabi Hindus. 

They were divided into 7 sub-castes of Saraswat Brahmins from the Punjab region. 

The  Hussaini Brahmin is a Mohyal Brahmin community of the Punjab-region, they have adopted non-Indic traditions. This has led to a small sub-set of the Moyhal community paying reverence to Islam, most notably to the third Imam Hussain. 

Society and Religion of the Baidya Caste

The Baidya or Vaidya are a Hindu people who live in northeast India and

Bangladesh. Their traditional occupation is being physicians. Vaidya means one who knows, studies and teaches the Vedas, the Hindu Scriptures. The Baidya are one of the highest Hindu castes equal to the Brahmins in India and Bangladesh. Baidyas' place in caste-hierarchy follows Brahmins — they wear the sacred thread, and have access to scriptures, but cannot conduct priestly services.  

The kings from the Sena dynasty of the 11th and 12th centuries were Baidya. Besides being medical doctors, the Baidya served as high-ranking military officers and as royal advisers. They were often given large tracts of land due to their service to the king. 

Today the Baidya continue to become physicians. Frequently, they are trained in both traditional Indian Ayurveda and Western medicine. 

The primary language of the Baidya is Bengali. As educated Indians and Bangladeshi, they also speak English and Hindi.

The Baidya pay special reverence to Vishnu, the preserver god and Surya, the sun god.