i have learned from a few mechanic friends of mine some simple easy way to clean certain things in cars. 

windows and windshields.  A lot of people are buying micro fiber clothes to do this, or pay professionals to clean the oils that build up on glass in cars.  i have been informed by a family friend who owns a chevy dealership that for the last 40 years they have used windex spray and news paper to clean the glass on the cars.  i have watched it get done, and the results are amazing.    just watch out for ink that bleeds, and don't think one sheet will work for the whole car.

carpets and seats.  it's easy to let the seats and carpets in your car go.  i personally have spilled soda and got stains all over the passenger seat.  a quick fix is resolve carpet cleaner.  (test it on a spot that isn't normally seen though.  i have seen resolve fade the colors on seat cloth before.)  if you don't want to risk using resolve get a normal carpet cleaner with a hand attachment.  they work wonders. for sweeping the carpets?  just use your family vacuum.  use a hose attachment, also make sure to put something under the vacuum itself so the bristles aren't getting destroyed by pavement, concrete etc.

gunky oil?  Pour in some seafoam.  it's a great product that conditions oil and gas.  it also clean out oil deposits.  i've seen in shops oil that comes out thinker than corn syrup.  some mechanics will dump a whole can into the crank case. 

dust on the dash?  don't drop the money on a can of armor all wipes.  just get a thing of baby wipes.  it works just as well and is cheaper too.  as long as you don't mind the baby wipe smell.