I just found this incredible article via digg and had lots of fun reading it. I really recommend for you to read it and get some good concepts in your toolbelt.

The top 10 concepts are:

  1. Interfaces

  2. Conventions and Templates

  3. Layering

  4. Algorithmic Complexity

  5. Hashing

  6. Caching

  7. Concurrency

  8. Cloud Computing

  9. Security

  10. Relational Databases