The discussion The specified item was not found. includes some suggestions for Internet math resources. Illuminations has many lessons for geometry grades 9-12. Here are a few ideas:
Also Iluminations has a site called Geometry Web Links that has a collection of annotated websites offering teachers and students information related to geometry and practice in using geometric concepts.
I did a search in Thinkfinity in the Classroom for geometry as the keyword and filtered grades 9-12. I found 128 Thinkfinity resources. I suggest you try this search and see what lessons, interactives, worksheets, etc. may be useful in your teaching.
Let us know if you are looking for specific geometry lessons. The Illuminations interactives for geometry such a the Interactive Geometry Dictionary: Lines in Geometry are awesome. You may want to explore the complete list of 39 Illuminations Geometry Interactives which use the Internet.
One other suggestion is to join one or more of the mathematics groups in the Verizon Thinkfinity Community and read through some of their discussions. You also can post discussions specifically related to geometry within a math group. To locate the math groups, use the Browse All tab on the gold navigation bar and select Groups. This will take you to the Groups directory where you can search for mathematics groups that you might enjoy joining.
I will agree that there are some really neat ideas at the Illuminations site and I do plan to use some of these. I am new to the Thinkfinity site and it is a bit overwhelming at first but I am slowly working my way through some small pieces of it.
Thank you for your suggestions!
In reference to collaborating with other teachers online, I suggest you try Skype in the Classroom. There are several discussions in the community about using the Internet to connect classrooms online.
If you find other ways to connect your geometry students with other geometry classrooms, please share them with us.
I'm not high school, but I'm fond of the National Library of Virtual Manipulatives.
What a great resource! I had not seen the National Library of Virtual Manipulatives website. That's a great list of interactives for all grade levels. Thanks for sharing.