Cool facts about bats:

Bats are mammals in the order Chiroptera, which means hand-wing. Bat fossils have been discovered from as long as 50 million years ago, but they are structurally very similar to bats of today.

All living bat species are generally classified as either Megachiroptera or Microchiroptera
Megachiroptera are known as flying foxes or megabats—they tend to be larger than microbats.  Large eyes cause them to resemble dogs or foxes, hence the name flying foxes.  They are only found in the Old World tropics.
Microchiroptera are found worldwide and vary substantially in appearance. These bats tend to use echolocation, and will be the focus of much of this website. Alternative methods of classification are discussed in Evolution

There are 1100 species of bats—a quarter of all mammal species
The bumblebee bat of Thailand weighs less than a penny while some flying foxes have a wingspan of up to six feet
Bats are long lived—some live for over 30 years

Most eat insects, but some eat nectar, fruit, small vertebrates, and blood.

Bats are useful to humans for many reasons including insect control, pollination, seed dispersal, reforestation, and navigational research

Images used with permission from Lollar

Some myths about bats:

Myth: Bats are blind
Fact: Many have very good vision.  Flying foxes forage for fruit using their large eyes.

Myth: Bats live in caves
Fact: Many inhabit trees, leaves, burrows, flowers, and spider webs!  They generally only inhabit buildings if alternatives are unavailable.

Myth: Bats are a major source of rabies
Fact: Bat rabies account for only one human death per year in the US.  Dog attacks account for more deaths annually than bats do in a decade

Myth: Bats can transmit West Nile Virus to humans
Fact: Only mosquitoes can pass WNV to humans and bats eat mosquitoes, so they can actually help prevent cases of WNV

Myth: Bats are closely related to birds
Fact: Although both fly, they evolved the trait independently.

Myth: Bats are closely related to mice
Fact: They are not closely related to rodents at all. Bats are placed in their own unique order, Chiroptera.

Myth: Bats get tangled in hair
Fact: The echolocation system of bats allow them to navigate much more complicated situations than the presence of a human. Bats swooping towards humans are likely more interested in the insects that tend to follow humans around (i.e. mosquitoes) than the actual person.

Myth: Bats are dirty
Fact: They spend much time grooming to keep their fur soft

("Natural History of Bats" and "Myths and Facts")