What law or which specific group of people has made the decisions
leading to the specific ways in which the security at airports have
increased since 9/11?  Which company (or companies) supply this
security (with their contact information)?  How much does this cost on
a yearly basis?  Where does the money come from to pay these
companies? To which places can you effectively complain/speak out if
you feel like the security is going too far and trampling on civil
liberties?  Are there any airlines/airports that offer pre-911
security for those who feel comfortable with that?

If you are asking about The USA, some of the details of the homeland
security law were likely written by rich and powerful persons, other
details were requested by President Bush and several members of The
USA House and Senate. The bill passed and was signed by President
George W. Bush. Your suggestions and complaints should be sent to your
member of Congress = House and your two Senators. This may be
effective as revissions are being considered. Wording should be
concise and polite. You might be wise to have several people somewhat
sympathetic to your opinion read and make suggestions about wording.
 Most of the direct costs are bourne by the USA tax payers, indirect
costs from airline profits, fare increases and quality of service
reductions. My main complaints with Homeland Security are: they need
to do more profiling of persons likely to be terrorists, and they are
not asking the public to assist, except very passively.   Neil

I don't know about you feeling comfortable with pre-9/11 security; but
I'm sure any "evil-doers" out there would feel VERY comfortable with
it!

If you want to look at Europe then both the European Regional Airlines
Association and the Association of European Airlines have recently put
out press releases based on the added costs that their members face
due to the increased security - unlike in the US it's not paid for by
the state:

http://www.eraa.org/system/id.asp?intid=1390

As for "going back to pre-911 security" I don't think legally (or
morally?) you'd get away with it.

Here's the link to the European Commission's study into "European
Civil Aviation Security Financing" - it includes comparisons to the
way things are done on the other side of the Pond....

http://www.europa.eu.int/comm/transport/air/safety/studies_en.htm