Rachel Cagle uses her Capitol Hill apartment building’s online tools to contact neighbors, request maintenance and find a baby sitter for her daughter, Eileen, 3.

How many renters does it take to change a lightbulb? None! There’s an app for that.

While sipping a smoothie at Starbucks one morning, Rachel Cagle remembers that a light is out in her Capitol Hill apartment. She opens the BuildingLink app on her iPhone, enters a request to replace the bulb and clicks send.

“Done,” the Senate Square Towers resident says. “By the end of the day, it will be replaced.”

Just as the bank and travel industries have gone mobile, so, too, has the business of apartment living. Buildings across the D.C. area are making the lives of their residents a little bit easier and a lot more fun with computer programs that can manage package deliveries, facilitate maintenance requests and even create a virtual social scene with personal profile pages similar to those on Facebook.

Case in point: When a package arrives at Senate Square (201 I St. NE, 866-963-3056), nobody gets a phone call or note in the mailbox. Instead, the concierge scans a bar code and the resident is automatically sent a notification email. In a building with so many young professionals, “nobody wants to be called when they’ve got a package,” says property manager Mark Hannon.

“The technology becomes the DNA of the building,” says Zachary Kestenbaum of BuildingLink, which creates the software Senate Square uses.

In addition to handling package deliveries, the software allows residents to do such things as reserve loading docks, arrange for guest parking and even send a photo of an ex-boyfriend to the concierge to keep unwanted visitors out.

In addition to the operational services, BuildingLink and other software similar to it offer residents a safe and private virtual world to get to know one another better.

Sang Park, a vice president of Vornado/CES, says his team initially planned to use Facebook to help residents connect and buy or sell belongings, but they wanted more privacy. His properties, including West End 25 (1255 25 St. NW, 888-217-2525) and 220 Twentieth Street (220 S. 20th St., Arlington, 888-769-6855), use a program called MyBuilding. “It’s been really surprising to me to see how many people use it,” he says.

Like Facebook, MyBuilding lets residents create a profile, look up information about one another and send messages on their building’s intranet.

MyBuilding’s CEO, Guy Blachman, says these programs create a community, and that’s why buildings pay for them. “Research shows that if there’s a better sense of community, then retention is greater,” he says.

Since Senate Square began using BuildingLink, Cagle says she’s seen “more camaraderie” in the building. Neighbors now send out emails about impromptu barbecues on the roof deck, and Cagle even found a baby sitter for her 3-year-old daughter through a posting.

Beyond the maintenance requests, new friendships and package notifications, these websites help residents fulfill more basic needs, such as ordering pizza. Shannon McGuire, a 220 Twentieth Street resident, uses her building’s website to search for restaurants that deliver in her neighborhood and read reviews written by other residents.

“It’s like Yelp, Yellow Pages, Google — everything — rolled into one,” she says.