The Oregon state website has a form through which you can email your senate and house representatives: http://www.leg.state.or.us/writelegsltr/
Postal mail
If you know your district number, here is a list of state representatives, and here is a list of state senators. Each page contains addresses and phone numbers.
Other ways?
If you want to post other ways to contact your representatives, please create an account, and then edit this page!