Just installed Elluminate on linux and I'm not entirely sure how I did it.
I went to a link posted by my maths tutor to an up-coming online tute and clicked to join. Firefox said here, run this file using java, I said OK. Lots of files were downloaded by java edk/sdk or something and then a chatroom opened up.
I guess you need to have java(yes I know there are proper instructions around) installed for it to work. This was good and easy though, two clicks and it's all worky, sweet!