I've had this problem recently. I'm doing a 366 photo-a-day project this year and sometimes, with work and everything, you don't get time to go outside and do photos, you just have to come up with something at home.
When you sit down and start to think creatively there are thousands of things you can photograph.
People, there must be family members, you can do portrait shots, candid shots, shots of them doing stuff, whether that be cooking, playing, being creative. You can do shots of them in their environment, close-ups of them doing something, macro shots of their face, hands, feet, holding stuff, working on stuff.
If all else fails how many different types of self-portraits can you shoot, reflections of yourself in different objects?
pets, portraits, activities, in the garden, sleeping, eating, environment, toys
your car or bike, on the drive, in the shed, detail shots of the badge, light clusters, dashboard, interior, how many ways can you light it, water drops on the bonnet, reflections in the chrome
collections - lots of people collect stuff, can you catalogue them? show items in unusual locations, for instance on the garden rockery
if you have a macro lens you open up so many other possibilities, creating art from everyday objects, cutlery, rusty tools, play with depth of field, focus stacking, guess the object.
what can you see from your house, landscapes, roofs, sunsets, the moon & stars?
Rooms, can you practise lighting a room to make it like an architectural/brochure shot.
I was with my daughter yesterday out in the countryside, we parked beside an electricity pylon and after 2 minutes and about 1 photo my daughter said there was nothing to photograph. I tried to explain that you have to start thinking creatively. Over the 30 minutes we took photos of the pylon from all angles, photographed details shots of it's nuts and bolts, done a few landscape shots in different directions, shot some leaves on the ground, taken pics of passing cars using panning, done details shots of my car including the badge and reflections in the wing mirrors, put the camera on a slow shutter speed and just panned across the field to get arty green, white and brown coloured abstract shots, and we hadn't gone more than 10 yards.
Take a look at my 366 project Flickr page, I think I'm up to about 42 shots so far, 25 of them have been taken in, beside or from my house.
get into the creative mindset and there is no excuse not to find a subject within a few feet of you, wherever you are.
http://www.flickr.com/photos/glnphotography/