Before you dive headfirst into the ocean of web tools, there are some things you need to know:

1. Computers do not have unlimited space or memory.  Be aware of the difference between a downloaded application (such as Skype), which takes up a lot of memory, and a web-based application (such as a blog), which does not. 
2. If you have high-speed Internet access, you will be able to do a lot more than if you depend on dial-up access.  If you have high-speed and your students don't, and you embed a lot of widgets (like dictionaries, slide-shows, and clocks) on a blog, the blog will load very slowly when your students try to open it.
3. Play around with a tool before attempting to use it in a class, so that you will become familiar with it.
4. Always test your tool in the lab or on the computer where you plan to use it with your class.  Computers are not all the same!
5. Always have a Plan B.  Technology does not always work!

Good luck,

Nina