Here's a site i just discovered (in the same way Columbus discovered America---i.e., it was already there but i ran into it). It is a math dictionary for kids. Everything is interactive. There is a word bank that students can click on, which then takes them to a definition, as well as some interactive content that brings that definition to life. Verrrry handy at boosting the communication side of learning, using and most importantly, UNDERSTANDING math terminology.
Just a word of warning. The site requires Adobe Flash Player, which is a free download, but it may need to be installed on your computer. It doesn't take long and is very handy for all sorts of web based content.