I agree with Ben on Craigslist for sure. Trulia also has rentals! I found my rental from a interdependent website which is another option. That is what stinks about rental listings they are just all over the place.
For a house though renterswherehouse.com has the biggest market share I believe. Good luck to you!
Often times, investor clients will inform me when their rental properties will be vacant. So it's just good to network and talk to anyone that is plugged in to the communities you wish to reside in. I would also check with the Stillwater Area Chamber of Commerce.