Haidian may be Beijing's technology and university district, but there's a lot of Old Beijing left here. Before you leave your hotel, ask for a boxed lunch (or grab some food at a nearby supermarket). Jump in a cab and head for the Summer Palace. Saunter around the lakes and ancient pavilions, and finally settle down somewhere secluded to enjoy a picnic.
When you're done with lunch and sightseeing, hop a cab to Hailong Shopping Mall. Go in and explore—the five-story shopping mall has every kind of computer or electronic device you could possibly want, often at deep discounts. Be careful when buying software, though, as most of it is pirated and illegal to bring back to the United States.
After you've shopped and you're ready to drop, head over to the Wudaokou Binguan for a selection of wonderful "snacks" that usually add up to a great dinner, and don't miss the zhapi, or mugs of fresh-from-the-tap beer. Taxi it on home in the wee hours.