Unlike doors, windows are supposed to be see-through, sometimes shatter when slammed, and don't always have a pizza delivery guy on the other side. Look after unattended glass panes with today's Groupon: for $50, you get $100 worth of window cleaning from Dr. Glass Window Washing. This Groupon is valid for customers in Washington, DC, as well as Howard and Montgomery Counties in Maryland.

CNN, The Washington Post, and USA Today all recognize Dr. Glass Window Washing for its refined methods, empowering business model, and meticulous attention to detail. Two- to three-hour glass-bathing sessions commence with an assessment of single-pane windows ($10 each) and sliding glass doors and casements ($6 per panel) for nooks, crannies, and cross-dimensional grime portals, and special considerations are made for storm-pane systems ($10 each) and house alarms. A $4 additional charge applies for extra small-paned windows.

Tender hands buff glass dry with surgical nonlint towels, which do not leave the unsightly specks that used handkerchiefs and toilet paper do. When cleaning interior surfaces, the window washers check shoes at the door out of respect for home interiors, since their high-tech squeegees are still not yet configured to sweep carpets of any pile height.