I received this information on Dua's for my post yesterday on 3 parts of Ramadan.
FIRST ASHRA (first ten days [1-10]):
The first ten days of the Blessed Month of Ramadan are the days of Mercy. We should seek Allah's Mercy in these days.
Rab-bigh-fir war-ham wa Anta Khair-ur-Raahimeen. (Surah Al Muminun:118)
("My Lord! Forgive and have mercy, for You are the Best of those who show mercy!")
Ya Rabb, Allahumma arhamni Ya Arham-mar-Rahimeen.
Ya Hayyu Ya Qayyumu Birahmatika asta-ghee-thu
SECOND ASHRA (second ten days [11-20]):
The second ten days of Ramadan are the days of Forgiveness, Seek Allah's forgiveness and repent for all sins.
Allahum-magh-fir-li dhunoobi Ya Rabbal Alameen
Rabbana Fagh-fir-lana dhunoobana wa kaf-fir-'anna sayyi-aatina wa ta-waf-fana ma-'al abraar. - Surah Al-Imran:193
(Our Lord! Forgive us our sins and remit from us our evil deeds, and make us die in the state of righteousness along with Al-Abrâr (those who are obedient to Allâh and follow strictly His Orders).
THIRD /LAst ASHRA (last ten days [21-30]):
The last days of Ramadan are to seek Refuge in Allah from the Hellfire.
Allahumma Ajirna min-an-naar.
(O Allah, protect us from the fire.)
DUA for LAYLA-tul-QADR (to be read in the last ten days):
Allahumma innaka 'affuwan tuhibbul 'afwa fa'fu'-anni
(O Allah, You are Most Forgiving, and You love forgiveness; so forgive me)
YA Ghufooru Ya Ghafooru Ya Ghafoor
(O Forgiver, O Forgiver, O Forgiver)