1. Trulia Trulia is my number one recommendation for finding rentals in Carlisle, PA as it often has more rental listings than it's parent company, Zillow.
2. Homes.mil Carlisle is home to the US Army War College Carlisle Barracks campus. Many owners will list exclusively on military housing websites instead of to the general public. The Army War College housing office refers renters to homes.mil and civilians are able to view these listings.
4. Facebook Marketplace An increasingly more popular location based rental advertising platform that all but eliminates Craigslist.
5. Good ol' Google In today's dynamic online age, there are always new entrants and fading establishments in the rental search industry. Instead of going to a specific rental listing site, let a basic Google search for rentals in the area you wish to live do the work for you. Using Google Maps can also help you find local rental agencies, property management companies, and Realtors who may have listings not found on the "Apartments.com"s of the world.
Valuable real estate search tools that also might help:
Zillow.com - Similar to Trulia but with fewer listings. Also associated with Hotpads.com. Good iOs / android apps.
AHRN.com - My second favorite website for Army War College / military focused listings
MilitaryByOwner.com - Great military housing site, but fewer listings because due to advertising costs.
NextDoor.com - Community based listings like Facebook Marketplace
WalkScore.com - Good for walkers, bikers, and neighborhood info.
AreaVibes.com - Rate your neighborhood by categories you choose.
I am always expanding this collection with rental resources I think will be useful to renters. If you know of a resource that might be useful, please submit it for consideration. Thanks!