Seeking forgiveness from Allah, repentance

أسْتَغْفِرُ اللَّهَ وَ أتُوبُ إلَيْهِ
Astaghfirullaha wa atūūbu ilai(hi) (I seek the Forgiveness of Allah and repent to Him.)
[to be reicted 100 times during the day] [Sahih al Bukhari, Muslim 4:2075]

http://www.islamawareness.net/Repentance/repentance.html

Duas for Asking for Forgiveness from God
http://www.soundvision.com/info/islam/forgivenessdua.asp

More duas for repentance
http://www.islamawareness.net/Dua/forgiveness.html