Here are links to some great sermons about the spiritual world and the spiritual battle.
Some basics
The Nature of the Battle part 1 (audio, 25 minutes long)
The Nature of the Battle, part 2 (audio, 25 min.)
The War Revealed and Strongholds Defined (video, 29 min.)
Finding victory over Satan's tricks and traps (video, 44 min.)
Take authority over the spiritual warfare in your life (video, 28 min.)
How the enemy tries to distract you from God's plan (video, 50 min.)
Overcoming Satan Series
How to Overcome Spiritual Warfare with the Armor of God (audio, 57 min.)
The Powerful Weapon of Peace (audio, 47 min.)
Overcoming Satan's Strategy Through Faith (audio, 41 min.)
Well-dressed for Warfare (audio, 49 min.)
Armor of God
The Belt of Truth (video, 31 min.)
Breastplate of Righteousness (video, 31 min.)
The Shoes of Peace (video, 32 min.)
The Shield of Faith (audio, 25 min.)
Helmet of Salvation, part 1 (audio, 25 min.)
Helmet of Salvation, part 2 (audio, 25 min.)
Sword of Spirit, part 1 (audio, 25 min.)
Sword of Spirit, part 2 (audio, 25 min.)
Igniting Kingdom Prayer Series (all are video, 28 minutes long each)
Another Prayer series (may be out of order, video, 28 minutes long each)
Random:
It's time to get serious about your relationship with God (video, 28 min.)
God is going to equip you to get you through (video, 28 min.)
The Secret to Powerful Prayer (video, 31 min.)
The Protection of Prayer (audio, 25 min.)
Experiencing Spiritual Deliverance (audio, 48 min.)
Defeating The Enemy with Prayer (audio, 49 min.)
Prayer that wins the war (audio, 28 min.)
The Power of Truth (video, 27 min.)
Using Prayer to overcome spiritual warfare (video, 28 min.)
Tearing down personal strongholds (audio, 25 min.)
Defeating the giants in your life (video, 30 min.)
