Every now and then you get an email that you just have to forward to several friends. That's not a big deal really but unless all of those friends are also relatives, you shouldn't ever put all their addresses in the "To:" line. Why? When you put all the addresses on the "To:" line they're all contained in the email, that's why. All your friends have to do to see the addresses in your email is to hit their "Forward" button. Here's a screenshot of a typical forward where all the addresses were on the "To:" line. This is what I saw on my screen when I clicked on the "Forward" button (I've changed all of these to bogus names and addresses):

Even though the sender probably had no such intention, he/she has shared all of these addresses with everyone on this list and if these folks aren't family, or very close friends, that's a rude, disrespectful and insensitive thing to do. Come on now, tell the truth, do you want your friends thinking you're rude, disrespectful and insensitive? I figure it's more than likely that a person could lose a lot of friends that way. What do you reckon? *grin*.
So, here's an alternative for you: It's called Bcc. That stands for "Blind carbon copy" and, as you might have guessed from the words, the concept has been around a lot longer than the Internet, or, for that matter, computers. It dates back to the days of typewriters and what it amounts to is sending a copy of a letter (i.e. email) to other (make that "multiple") persons without their names and addresses appearing in the letter (email).
I'm going to show you how to use this feature in Outlook Express but every email client I know anything about has this feature so you should be able to find a tutorial by typing the name of your email client, a plus sign, the letters "bcc", another plus sign and the word "tutorial" into Google. That might, for example, look like this:

When I ran this search I found a good tutorial for using Bcc in Pegasus on the first page of results. Substituting the name of any other email client should work at least as well. Ok, moving right along.....
In Outlook Express,open the email you want
to forward and click the "Forward" button.

Delete all sensitive and/or superfluous
information at the top of the email.

Click on the "To:" button
next to the address bar.
(This will open your address book)

Select an address and click on the Bcc button.
Repeat for everyone to whom you wish to
forward the email, then click on the "OK" button.

That's it, your email is ready to send.
If you just can't stand to leave to "To:" line
blank, you can type in your own address.

If the email is full of forwarding arrows you might have a look at my
email cleaning tutorial before you move on.
This tutorial, by Don Crowder, posted on December 27, 2005
Addendum 10-18-2006: Here's a way to make forwarding email via Bcc even easier in Outlook Express. Click on the "Create Mail" button to open a new email. Once the email window opens, click on "View" (at the top of the window), and click on "All Headers". Notice that a Bcc adress line has now appeared under To: and Cc:. Once All Headers has been selected the Bcc line will appear by default in all new emails, replies and forwards.