Possible topics:
- Harry's development as a person throughout the years
- That there are things worse than death
- That the division between wizards/witches and muggleborn wizards/witches has parallels to the real world
- The ways in which Voldemort terrorized everyone
- The value of facing up to one's enemy
- What influenced Harry most (eg. dead parents, Weasleys, Dumbledore, Sirius, Dursleys)
- How Rowling shows that courage and hope can come from the most unlikely places
- Whether the division of Hogwarts into houses is productive and ethical
- How the wizarding world hides from the muggles
- The circumstances surrounding Voldemort's Death Eaters (their background, willingness etc.)
- Whether good always prevails
- The value of sacrifice
- The relationship between the Dursleys and Harry
- How the value of love is reiterated throughout the series
- Harry's flaws
- Importance of Quidditch to the wizarding world
Hope this helps

Frederick
Harry Potter nerd and founder of HP website http://www.mugglemix.com