The theory for the ending that I've seen the most is:
At the credits ending of Cloverfield, *spoilers* the audio from the video cam says, "Help us!".
But when played backwards, it says, "It's still alive!" This happens after the end credits
of Cloverfield. Assuming the speaker was Rob, he suggests Cloverfield (the monster)
is still alive. This also suggests a sequel for Cloverfield 2! *Spoilers*
The Japanese oil company TAGRUATO drops a satellite (Chimpanz III) into the ocean as part
of viral marketing (shown at the end of the movie when Rob and Beth were on the ferris wheel).
TAGRUATO works with SLUSHO (a slush company), as the main ingredient for SLUSHO is found
at the satellite dropzone (deep ocean). While searching for satellite and ingredients, they
woke Cloverfield (the monster).
People who were at the party in the beginning of the movie, were seen wearing SLUSHO shirts.
Rob apparently was going to be the Vice President of TAGRUATO in Japan.
The main ingredient of Slusho apparently turns a tiny fish into a HUGE whale, which explains
the size of Cloverfield. *Update* The main ingredient is a deep sea nectar.
For animals/fishes/insects to survive in the deepest ocean (very high boiling temperature),
they naturally have very high heat resistance. This explains how Cloverfield is able to
withstand numerous bombs and attacks from the army.
Cloverfield refers to the field formerly known as Central Park. Clovers are
usually prone to grow at places after bombing. Thus the term "Clover" and "field" referring to park.