Base antennas.

Base types come in many different sizes and shapes to allow for different situations and price ranges.

Some are a straight single pole, while others may be two poles or have several legs on. For those with limited space or no access to the roof, some are designed to fit in a loft. Some of the best types may be large and obtrusive, so some people may want a smaller antenna.

A cheap, but reasonable type which does not look to bad is the dipole. These are mounted in the middle, so only have 9 foot above the mounting point (with another 9 foot below that point).

There are also many makes of cheap straight antennas which perform quite well. Be careful with cheap straight types, as these can often bend and break in strong winds.
The cheapest option of all is to make your own antenna out of wire or coax. This can be hung from a part of the building or a tree.

There are several ways to mount a base station antenna, more details on the base mounts page.