My biggest challenge is to manage the classroom papers. Like many schools they want us to go Paperless!
Edmodo is great! The secret is to have your student submit projects as PDF's. They load fast and you can annotate them in Preview--it works slick and with the time stamp it is easy to prove when things are late. You also can't lose a paper. The quiz application is also works well in Edmodo.
Having a "Ning" is also helped me with my students to have a discussion board for students to get interacting. I emailed them and they found me a sponsor so I can have one for free.
Another site is JoinMe--it allows me to let a student see my screen or I can take control of their screen for free. It is very helpful when you are not in the same room or anywhere. Works great.
Textbooks are still not what I want--I'm hoping they can come up with a textbook that is more than just a PDF and is interactive.
Finally--I teach HS and they still love to use markers and paper to create. Don't forget that staring at a computer screen all day is boring.
Good luck--if you want some great Web 2.0 tools check out my presentations at the following link http://https://sites.google.com/a/crcsd.k12.ia.us/crbusinessdept/home/teacherpresentations