Windows:
Layers of dirty film on windows and screens provide a helpful filter
against harmful and aging rays from the sun. Call it an SPF factor of 15
and leave it alone.

Cobwebs:
Artfully draped over lampshades reduce the glare from the bulb,thereby
creating a romantic atmosphere. If someone points out that the light
fixtures need dusting, simply look confused and exclaim "What? And spoil
the mood?" (Or just throw glitter on them & call them holiday
decorations.)

Pet Hair:
Explain the mound of pet hair brushed up against the doorways by claiming
you are collecting it there to use for stuffing hand-sewn play animals
for underprivileged children. (Also keeps out cold drafts in winter.)

Guests:
If unexpected company is coming, pile everything unsightly into one room
and close the door. As you show your guests through your tidy home,
rattle the door knob vigorously, fake a growl and say, "I'd love you to
see our den, but Fluffy hates to be disturbed and the shots are SO
expensive."

Dusting:
If dusting is REALLY out of control, simply place a showy urn on the
coffee table and insist that "This is where Grandma wanted us to scatter
her ashes."

General Cleaning:
Mix one-quarter cup pine-scented household cleaner with four cups of
water in a spray bottle. Mist the air lightly. Leave dampened rags in
conspicuous locations. Develop an exhausted look, throw yourself on the
couch and sigh, I clean and I clean and I still don't get anywhere." As a
last resort, light the oven, throw a teaspoon of cinnamon in a pie pan,
turn off oven and explain that you have been baking cookies for a bake
sale for a favorite charity and haven't had time to clean... Works
everytime.

Another favorite, I think from Erma Bombeck...

Always keep several get well cards on the mantle so if unexpected
guests arrive, you can say you've been sick and unable to clean.