You can buy TM's in:
- Icirrus City! The TM's are Blizzard, Thunder and Fire Blast.
- Nimbasa City! The Tm's are Frustration, Return, Thunder Wave, Gyro Ball, Light Screen, Safeguard, and Reflect.
- Mistralton City!: The Tm's are Hail, Sunny Day, Sandstorm, and Rain Dance.
You can also get TM's by using BP in the Battle Subway.
The shopping mall on route 9 has some pretty powerful TM's as well. Hyper Beam and Giga Impact!
Hope this helps =)