In countries where Theravāda Buddhism is practiced by the majority of people, such as Sri Lanka, Cambodia, Laos, Burma, Thailand, it is customary for Buddhists to hold elaborate festivals, especially during the fair weather season, paying homage to the 28 Buddhas described in the Buddhavamsa. The Buddhavamsa is a text which describes the life of Gautama Buddha and the 27 Buddhas who preceded him. The Buddhavamsa is part of the Khuddaka Nikāya, which in turn is part of the Sutta Piṭaka. The Sutta Piṭaka is one of three main sections of the Pāli Canon of Theravāda Buddhism.

The first three of these Buddhas—Taṇhaṅkara, Medhaṅkara, and Saraṇaṅkara—lived before the time of Dīpankara Buddha. The fourth Buddha, Dīpankara, is especially important, as he was the Buddha who gave niyatha vivarana (prediction of future Buddhahood) to the Tibetan-Burmo youth who would in the distant future become the bodhisattva Gautama Buddha.

The 29 named Buddhas

1 Taṇhaṅkara

2 Medhaṅkara

3 Saraṇaṅkara

4 Dīpankara

5 Koṇḍañña

6 Maṅgala Brahmin

7 Sumana Kshatriya

8 Revata

9 Sobhita

10 Anomadassi

11 Paduma

12 Nārada

13 Padumuttara

14 Sumedha

15 Sujāta

16 Piyadassi

17 Atthadassi

18 Dhammadassī

19 Siddharttha

20 Tissa

21 Phussa

22 Vipassī

23 Sikhī

24 Vessabhū

25 Kakusandha

26 Koṇāgamana

27 Kassapa

28 Gautama

29 Maitreya -Buddha of the future.. (to be born in the future)

More Info: en.wikipedia.org