Living / Family Room
It's time to get rid of the old sofa and, yes, even that favorite recliner that your father-in-law falls asleep in every time he visits. If new furniture is an option, great! But if it isn't, look for some great furniture covers. Furniture covers can change the whole look of a room for a fraction of the cost of new furniture, and the recliner will still be just as comfy. If you happen to have both a living room and a family room, try switching the furniture around. You probably spend more time in one room than the other and switching the furniture between the two rooms every so often will make them both last longer and give you a new look to work with.
Have your carpets cleaned and paint the walls. Don't be afraid of color! The best interior decorating experts will tell you that white walls are boring. Take a swatch from the furniture, or a throw pillow, and find paint that matches one of the colors in it. Make sure not to use the primary color of the furniture on the walls, you don't want them to blend. You do want good contrast. Get some new window dressings and nic-nacs and your room will look like brand new.
Interior decorating in the kitchen is a bit more difficult, but there are a few ways to make it look new. Start with some new window dressings, a throw rug under the table, and a nice new border on the freshly painted walls. If that's not enough, you could paint your cupboards and install new handles and pulls, or remove the upper cupboard doors if it's not too much of a mess inside. This will make your kitchen look much larger and more open. A nice, new faucet goes a long way in a kitchen,
Bathrooms
There's not much interior decorating that can be done in a bathroom without replacing the fixtures. You can certainly replace the shower curtain, window coverings, accessories, and toilet covers and rugs.