I just bought a new Compaq Presario (R3000). I am using it to give 
presentations to groups via a projector - Not more than 50 people
typically, but more than a handful. The projector only has a mono
speaker, and of course the laptop speakers are very small and can't
project with any volume.

The only output button I see on the laptop is for a headphone,
although it has ethernet ports, Firewire etc...

If I am giving a presentation to a group and need stereo sound for
certain parts of the presentation, how do I hook up external sound and
speakers. Do I use the headphone line out, and if so what type of
Amplifier will be required. Or is there some more likely way such as
using the USB ports to export my sound. I know it must be a common
issue-needing sound much louder than the laptop can provide, but I am
at a loss as to how it should be done

Hello,

As the system already have a headphone socket, you could use any kind
of stereo amplifiers available. Then connect the amp through headphone
pin and correct the volume to your choice. Another way is to use
external audio devices like Creative Extigy, where sound is
transported via USB.
Visit www.soundblaster.com

Just buy any set of computer speakers (or personal portable speakers)
with an external power supply, these are available at any electronics
store such as Best Buy, Circuit city, Target etc.  I would buy a two
speaker set that does not have a subwoofer (to remain portable) and is
of a decent quality, expect to pay $30 to $100.  These all connect to
the headphone output, which is stereo and are suitably amplified for a
laptop output.

Thanks to both tuning and rennaisanzmn,
Your answers are both very helpful! 
I really appreciate it. I'm going to close the question since this is
really what I needed to know.

I did this recently setting up both a Mac and a Windows machine using
the headphone jack as sound out to a Fender amp to the biggest
speakers I could find. We knocked their socks off! We did need a bunch
of power strips, heavy duty extension cable and tape to secure the
cables so no one tripped over them. Don't use duct tape because it
makes your cables all gummy and sticky. Gaffers tape leaves them a bit
cleaner.

What were you doing susanam, having a concert?  I don't need THAT much
sound. But if you can do that with a fender amp, then I should be fine
with a small powered speaker set.

I have a pair of wireless speakers made by RCA about 3 years ago,
About 3 rms watts each, with 4 new D cells in each. That may be
equivelent to 20 watts peak from computer speakers. The sound quality
is not excellent and dropouts occur occasionly more than 30 feet from
the 900 megahertz transmiter. It was about $140 for two speakers, the
transmitter and an adapter from Radioshack. I suspect a dozen other
brands, some better and some cheaper are available. WIreles means no
wires to trip over, but the D cells are down to low audio volumn in
about one hour.  Neil

I can'r remeber who sales it but there is a device you can buy for
around $100.00 and with it you can hook up any of your household
speakers to it.

You can purchase a $6 cable at Radio Shack that will turn an 1/8" jack
(headphone jack on your laptop) into RCA plugs like those found on
VCRs or Stereos. You just plug these RCA plugs right into the back of
your amp (most amps have spots for these) and then plus your speaker
into the amp and you're good to go.

You can also use this cable to play MP3's from your computer on your
home stereo if you choose. I find it easier than burning CDs all the
time.

Thanks!  I think I thought the signal from a headphone out was going
to be too weak, but with the amp (or powered speakers) all is cool!