Neighborly - The easiest way to invest in your community
NowRenting - Everything a landlord or rental agent needs in one web app.
Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...
Rentger - The most simple and useful property manager software.
Data Dashboard by Wikimedia Foundation - Compiled data of the Worlds busiest public site
Tellus - An all in one rental management app