Try Nonags or Softseek or Tucows or Strouds sites for freeware. The first thing you'll need is a good html editor . You'll also want an image editor to create or resize graphics and finally a program to upload your files. Get all of these, and a decent html reference and you're away. They are available from Nonags .
Lite version is free for educational use.
If you're looking for something else, or just want to know what's out there, try one of the software collections. If you know of any other software that you think other teachers might want to use, let me know .