A Real Estate Investment Trust (REIT) is a structured business that receives its income on rents from properties. Apartments, storage units and shopping centers are often organized as REITs.
NAREIT (Info Page) NAREIT is an industry group that follows and promotes the development of Real Estate Investment Trusts (REITs).
Equity Lifestyle Properties (Profile) ELS is an REIT that invests in RV resorts and mobile home communities (ie trailer parks).