RCT3 extended is a new community initiative to make rct3 content well-rounded and to come up with a single-stop place for custom content. You can get more details from this thread:
We are planning to start a website for the RCT3 Extended project. It would greatly help if you can volunteer to be part of the project or the website - to be part of the dream ( find more details about my *dream* in the above link)
If you are interested, please shoot a mail to "rct3.extended @ gmail.com" ( please note that spaces are included in the email id posted here, to evade web robots. While mailing me, please remove the spaces from the mail id ).
Waiting for your email ...