With the real estate investment trust (REIT) sector still well off its highs, now could be the time for investors to pick up shares that are trading at attractive valuations. After sifting through the sector I have found a few areas that are worth highlighting: shopping centres, college campuses, health properties and storage facilities.

We're going to explore four REITs most investors probably would not have considered because they each have a unique arena in which they do business. If you would like to gain exposure to the entire sector there is always the route of a REIT ETF, but for the investors that want a chance to beat the index here are four REITs to start. (To learn more, read What are REITs and Basic Valuation of A REIT.)

The Candidates
Acadia Realty Trust (NYSE:AKR) - This trust specializes in investing in and operating shopping centers mainly in the Northeast. The portfolio is currently made up of 77 properties, that the trust owns or has partial ownership in. It's a grand total of over 10 million square feet of shopping. Most of its shopping centers are filled with stores that provide necessities such as Wal-Mart and Walgreens. The current dividend yield is 3.4% and as of the last earnings release, it has a year-over-year quarterly revenue growth of an astounding 29.5%! Not bad considering the general slow-down we are seeing in the retail sector.

American Campus Communities
(NYSE:ACC) - Remember those small, cement dorm rooms from your college days? American Campus Communities was quite possibly the owner. The company also has its hands in upscale student housing. In all the company has housing projects in 22 states throughout the U.S. located on or near campuses. Owning real estate near a university is almost as good as beachfront; there will always be a need for housing. The stock pays a 4.5% annual dividend and has a year-over-year quarterly revenue growth of 26.2%.

Nationwide Health Properties (NYSE:NHP) - As the baby boomers age there will be an increased need for long-term care and healthcare related services. With NHP owning over 550 healthcare properties in 40 states it should see the demand for their building rise. The healthcare REITs have been the strongest of the sector and are my favorite long-term play of all REITs. Nationwide Health Properties can be looked at as best of breed, with a gross margin of 97.39%, a dividend yield of 4.9% and a quarterly year over year revenue growth rate of an astonishing 32.4%! (For related reading, check out Healthy Survival Guide For Sandwiched Boomers.)

Extra Space Storage (NYSE:EXR) - When you want to store your old couch because you moved into a new house or were forced to downsize, a storage facility will be useful. The company buys, develops and manages over 600 self-storage facilities throughout the country. Most people have used a storage facility at one time and will use them again; this is a great business model. With housing foreclosures occurring, and many people making the move back to smaller houses, the need for storage is increasing. At a growth rate of 24.4%, Extra Space Storage is seeing quarterly revenue growth of more than double its competitors. The REIT is trading off of its 52 week highs, and the current dividend yield is 5.9%, which makes it a good time to look at this one further. (For more examples of the areas to invest in, click over to our tutorial Exploring Real Estate Investments.)

The Bottom Line
The MSCI US REIT Index has bounced around quite a bit lately. Since it hit a high of 1,238.34 in February of last year, the index is down 25% overall. It hit rock bottom in January of 2008 at 755.21, and is now up 23% from that low.

After a decade of gains, the REIT sector was overdue for a pullback that took place over the last twelve months. Now that the sector has become attractive again, it is time to start putting some money back to work in REITs.

For further reading, be sure to see our related articles The REIT Way.