The National Zoo, part of the Smithsonian, has a webpagehs tons of fantastic things to do:

• videos
• live webcams to watch the animals (with activities to go along)
• games
• self-guided interactive learning
• quizes
• classroom activities

You could spend hours visiting the Zoo virtually! I enjoyed watching the naked mole rats (kind of ugly). The lions were kind of boring. They were just laying around doing nothing. I did the self-guided learning for Amphibians which had tons of information and some really outstanding photography.