Well, I have a husband who works two night shifts a week (is a SAHD while I work three days a week) and our flat is small so I clear out the flat with our 2 year old for about 5-6 hours a day on those days. We've done this since being back in London when she was 7 months.
Mind you, we're in London so there's plenty to do.
I tend to go to a playgroup and park in the morning, then sling her for a nap at midday either before or after a picnic lunch, then onto the train and tube to somewhere such as the Zoo, aquarium and walk down the South Bank, Science Museum, V&A (often have craft activities there) Natural History museum, Toy Museum, libraries etc etc.
My husband also takes her out every day from midmorning to midafternoon. And we both do this at the weekend. Say, some activity for her, nap in sling, lunch out for all of us and something nice in the afternoon.
Back at home it's crafts, playing and a bit of her addiction, Tom and Jerry.
I have only spent a day in doors when we all had swine flu.