There are many different kinds of ugly air conditioners, but if you have an upright "motel-style" A/C unit, you can keep it from being an eyesore by turning it into a stylish landing strip.
A landing strip is the small table that resides near the entrance to your home; the place you throw your keys, the mail, and other things when you come home. Even if your A/C unit isn't located next to the door, though, you can hide it (and give it further purpose) with a tabletop and a clever enclosure. The example at the top is enclosed in some laminate flooring, and enhanced with some small table legs under the tabletop to provide adequate airflow out of the A/C. It looks much better than the original unit, and now you have another surface in your home to store the knick knacks that come and go day to day.
Hit the link to read up on 9 other clever A/C and radiator hiding methods, and share your favourite tricks in the comments.
10 Ways to Hide an AC or Heater [Unplggd]