I have a LAN network in my office and I believe that some of my
employees are misusing their computers by discussing non-work topics
on AOL Instant Messager (AIM).  I want to know how I can use either a
program or my terminal to view all the network packages that are being
transmitted.  I have a Mac running OS X and have tried two programs:
Brian Hill's MacSniffer (find.macworld.com/0234) and Stairways
Software's Interarchy (www.interarchy.com) and have had the best luck
with Interarchy.

My problem is that everyone in my LAN, including myself, is connected
through wireless except for one computer that is connected through
ethernet to a router (I do NOT use this computer and only have Linksys
admin access to this router).  Is there a way for me to pick up all of
the packets that these other computers are transmitting on my network
and see specifically what they're saying on AIM as well as the sites
they visit and data they transmit over my network?  If advice is given
about using the terminal, please note that I have very little unix
knowledge.  Thank you.

First off, it may be a privacy violation to sniff the line.  Even
though the line should be used for business, I think it may be
analagous to recording people's phone conversations from work phones. 
I may be wrong on this, but you may want to check this first if you
haven't already.

I know this doesn't answer your question...but you could just have AIM
uninstalled from all the comps.  Of course, this doesn't eliminate
other, less-efficient communication means (windows net send, email,
phone, written notes, morse code, smoke signals, etc).  It may be more
efficient to let the chatting occur and maybe ask to keep it to a
minimum if you see the work output degrade.

Thanks for the heads up James.  I recently read that businesses are
allowed to monitor communications on their networks, and being that I
own the office, computers, software, and business, I believe that I am
allowed to monitor these communications.  These services I provide
(internet, computers, AIM, etc.) are all intended for work purposes
and I just want to keep it that way.  Unfortunately, some of our
clients prefer AIM as their communication since we need freaquent
updates, and eliminating AIM would only shut down one of many possible
ways to use the equipment for purposes other than work (as you have
pointed out).

If you are planing on doing this you might want to check into the laws
first as if you do not to it to the letter you may be held
accountable. Unless your employees know that you are going to be
monerting them then you will be breaking the law. You do not even have
the legal rights to spy on someone who uses your computer. So before
you decide to make this decision than you may want to contact a lawyer
and have everything approved ahead of time. Becuse if your employees
do not know that you may be spying on them then you can end up in
court for invasion of privacy, and yes even if they are your
computers.

I have consulted a friend of mine who is a lawyer and he says that I
should just have my employees sign waivers stating that they
understand the business intent of the machines and programs provided
and that I  reserve the right to monitor communications on these
machines.

The architecture of AIM by default has all mssages sent to the AIM
server where they are forwarded to the recipient. This is circumvented
when a user opens a direct connection in which case messages are sent
directly between the two aim clients. AIM messages are typically sent
in plain text, meaning if you were to use a packet sniffer on the
network and capture ALL traffic the AIM messages would appear in plain
text. Aim now supports encryption so a user could possibly use
encryption making it extremely difficult to decode their messages.

For more information on MAC OS packet sniffers check out:
://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2004-47,GGLD:en&q=mac+packet+sniffer

There is a program I have never tried called AIM SNIFFER which is
suppose to be able to sniff and capture only AIM traffic.  you can
check it out at:
http://www.programurl.com/aim-sniffer.htm

The fact that the network is wireless should only be a problem if they
are using AD-HOC networking (computer to computer) if not then you
should be able to capture all traffic after it leaves the wireless
router.

Other options you can explore are computer monitoring/keyboard capture
software to record keystrokes.  Very intrusive but it will keep
everyone honest.

Here's an interesting article about the issues involved in employee monitoring.

http://www.nysscpa.org/cpajournal/2004/704/essentials/p52.htm
Computer Monitoring and Surveillance
Balancing Privacy with Security