Following are a few Du'as that one should commit to memory or keep at hand for the month of Ramadhan:
اللَّهُمَّ إنِّى لَكَ صُمْتُ وَبِكَ آمَنْتُ [وَعَلَيْكَ تَوَكَّلْتُ] وَعَلَى رِزْقِكَ اَفْطَرْتُ
Allahumma inni laka sumtu wa bika aamantu [wa 'alayka tawakkaltu] wa 'alaa rizqika aftartu
O Allah! I fasted for You and I believe in You [and I put my trust in You] and I break my fast with Your sustenance.
or
ذَهَبَ الظَّمَأُ وَ ابْتَلَّتِ الْعُرُوقُ، وَ ثَبَتَ الأجْرُ إنْ شَاءَ اللَّهُ
dhahabadh dhama-u wabtallatil 'urooqu, wa tha-batal ajru insha Allah
The thrist is gone, the veins are moistened and the reward is confirmed, if Allah [Ta'ala] wills.
or
اللَّهُمَّ إِنِّي أَسأَلُكَ بِرَحْمَتِكَ الَّتِي وَسِعَتْ كُلَّ شَيْءٍ أَنْ تَغْفِرَ لِي
Allaahumma inni as-aluka birahmatika allati wasi'at kulla shay-in an taghfira li
O Allah, I ask You by Your mercy which envelopes all things, that You forgive me
Du'a to be recited in between every 4 Rak'ats of Taraweeh
سُبْحَانَ ذِيْ الْمُلْكِ وَ الْمَلَكُوْتِ
سُبْحَانَ ذِيْ العِزَّةِ وَ العَظْمَةِ وَ الهَيْبَةِ وَ القُدْرَةِ وَ الكِبْرِيَاءِ وَ الجَبَرُوْتِ
سُبْحَانَ المَلِكِ الحَيِّ الَّذِيْ لا يَنَامُ وَ لا يَمُوْتُ
سُبُّوْحٌ قُدُّوْسٌ رَبُّنَا وَ رَبُّ المَلَائِكَةِ وَ الرُّوْحِ
اللّهُمَّ أجِرْنَا مِنَ النَّارِ
يَا مُجِيْرُ يَا مُجِيْرُ يَا مُجِيْرُ
Subhaana dhil mulki wal malakooti
Subhaana dhil izzat wal azmati wal haybati wal qudrati wal kibriyaa-e wal jhabaroot
Subhanal malikil hayyil ladhi laa yanaamu wa laa yamootu
Suboohun qudoosun Rabbuna wa Rabbul malaaikati war rooh
Allahumma ajirna minan naar
Ya Mujeeru Ya Mujeeru Ya Mujeeru
Glorified is the Owner of the kingdom of the earth and the heavens;
Glorified is the Possessor of Honour and Magnificence and Awe, and Power and Greatness and Omnipotence;
Glorified is the Sovereign, the Living, Who does neither sleep nor die
O all Glorious, All Holy one, Our lord and the Lord of the Angels, And the soul.
O Allah save us from the (hell) fire.
O Saviour, O Saviour, O Saviour
Insha Allah, by reciting these Du'as one will get the rewards that lie in the month of Ramadhan.
When beginning the fast- Suhur
وَبِصَوْمِ غَدٍ نَّوَيْتُ مِنْ شَهْرِ رَمَضَانَ
Wa bi-sawmi ghadin nawaytu min shahri Ramadhan
I intend to keep the fast for tomorrow in the month of Ramadan
or
نَوَيْتُ أنْ أصُوْمَ غَدًا لِلهِ تعَالي مِنْ فَرْضِ رَمَضَانَ هَذَا
Nawaytu an asooma ghadan lillahi ta'aala min fardhi Ramadhana haadha.
I intend to fast tomorrow for the sake of Allah Ta'ala from the obligatory fasts of this Ramadhan.
or
نَوَيْتُ أنْ أصُوْمَ هَذَا الْيَوْمَ لِلهِ تَعَالي مِنْ فَرْضِ رَمَضَانَ
Nawaytu an asooma hadhal yowma lillahi ta'aala min fardhi Ramadhana
I intend to fast today for the sake of Allah Ta'ala from the obligatory fasts of Ramadhan.
or
اللهُمَّ أصُوْمُ غَدًا لَكَ فَغْفِرْلِيْ مَا قَدَّمْتُ وَ مَا أخَّرْتُ
Allahumma asoomu ghadan laka, Faghfirli maa qaddamtu wa maa akkhartu
O Allah, I am fasting tomorrow for Your sake, so forgive my past sins and future sins.
When breaking the fast- Iftar
وَبِصَوْمِ غَدٍ نَّوَيْتُ مِنْ شَهْرِ رَمَضَانَ
Wa bi-sawmi ghadin nawaytu min shahri Ramadhan
I intend to keep the fast for tomorrow in the month of Ramadan
or
نَوَيْتُ أنْ أصُوْمَ غَدًا لِلهِ تعَالي مِنْ فَرْضِ رَمَضَانَ هَذَا
Nawaytu an asooma ghadan lillahi ta'aala min fardhi Ramadhana haadha.
I intend to fast tomorrow for the sake of Allah Ta'ala from the obligatory fasts of this Ramadhan.
or
نَوَيْتُ أنْ أصُوْمَ هَذَا الْيَوْمَ لِلهِ تَعَالي مِنْ فَرْضِ رَمَضَانَ
Nawaytu an asooma hadhal yowma lillahi ta'aala min fardhi Ramadhana
I intend to fast today for the sake of Allah Ta'ala from the obligatory fasts of Ramadhan.
or
اللهُمَّ أصُوْمُ غَدًا لَكَ فَغْفِرْلِيْ مَا قَدَّمْتُ وَ مَا أخَّرْتُ
Allahumma asoomu ghadan laka, Faghfirli maa qaddamtu wa maa akkhartu
O Allah, I am fasting tomorrow for Your sake, so forgive my past sins and future sins.
When breaking the fast- Iftar
اللَّهُمَّ إنِّى لَكَ صُمْتُ وَبِكَ آمَنْتُ [وَعَلَيْكَ تَوَكَّلْتُ] وَعَلَى رِزْقِكَ اَفْطَرْتُ
Allahumma inni laka sumtu wa bika aamantu [wa 'alayka tawakkaltu] wa 'alaa rizqika aftartu
O Allah! I fasted for You and I believe in You [and I put my trust in You] and I break my fast with Your sustenance.
or
ذَهَبَ الظَّمَأُ وَ ابْتَلَّتِ الْعُرُوقُ، وَ ثَبَتَ الأجْرُ إنْ شَاءَ اللَّهُ
dhahabadh dhama-u wabtallatil 'urooqu, wa tha-batal ajru insha Allah
The thrist is gone, the veins are moistened and the reward is confirmed, if Allah [Ta'ala] wills.
or
اللَّهُمَّ إِنِّي أَسأَلُكَ بِرَحْمَتِكَ الَّتِي وَسِعَتْ كُلَّ شَيْءٍ أَنْ تَغْفِرَ لِي
Allaahumma inni as-aluka birahmatika allati wasi'at kulla shay-in an taghfira li
O Allah, I ask You by Your mercy which envelopes all things, that You forgive me
Du'a to be recited in between every 4 Rak'ats of Taraweeh
سُبْحَانَ ذِيْ الْمُلْكِ وَ الْمَلَكُوْتِ
سُبْحَانَ ذِيْ العِزَّةِ وَ العَظْمَةِ وَ الهَيْبَةِ وَ القُدْرَةِ وَ الكِبْرِيَاءِ وَ الجَبَرُوْتِ
سُبْحَانَ المَلِكِ الحَيِّ الَّذِيْ لا يَنَامُ وَ لا يَمُوْتُ
سُبُّوْحٌ قُدُّوْسٌ رَبُّنَا وَ رَبُّ المَلَائِكَةِ وَ الرُّوْحِ
اللّهُمَّ أجِرْنَا مِنَ النَّارِ
يَا مُجِيْرُ يَا مُجِيْرُ يَا مُجِيْرُ
Subhaana dhil mulki wal malakooti
Subhaana dhil izzat wal azmati wal haybati wal qudrati wal kibriyaa-e wal jhabaroot
Subhanal malikil hayyil ladhi laa yanaamu wa laa yamootu
Suboohun qudoosun Rabbuna wa Rabbul malaaikati war rooh
Allahumma ajirna minan naar
Ya Mujeeru Ya Mujeeru Ya Mujeeru
Glorified is the Owner of the kingdom of the earth and the heavens;
Glorified is the Possessor of Honour and Magnificence and Awe, and Power and Greatness and Omnipotence;
Glorified is the Sovereign, the Living, Who does neither sleep nor die
O all Glorious, All Holy one, Our lord and the Lord of the Angels, And the soul.
O Allah save us from the (hell) fire.
O Saviour, O Saviour, O Saviour
Insha Allah, by reciting these Du'as one will get the rewards that lie in the month of Ramadhan.