MSN has a nice article with some good links titled What realty agents won't tell you. It explains there are some pieces of information that an agent simply can't speak about due to fair-housing laws. That's where librarians come in; we generally can tell you by pulling up statistics, first-hand reports, and historical records. Sorry, if you're planning to move into a cheap apartment owned by a slumlord, crawling with gangs, close to being condemned; we won't stop you. However, you might note an anxiousness in our voice when we say, "I highly suggest you check out ARJIS" or "That is a very spacious area, lots of open fields, no houses, no playgrounds,.. no birds,.... no wildlife..... Geotracker is a site you might want to visit."
Real estate agents are knowledgeable professionals, and they will often tell you the same sites in much the same ways as librarians, but they deal on commission and have an obligation to protect the seller and seller's agent as well as to protect you. A librarian's obligation is to provide facts which help you make better decisions. Therefore, we might just hurt the interest of a slumlord or someone trying to sell a toxic waste dump.
