If you have a website of your own, Google AdWords is a great way to make money!  All you have to do is sign up, install a bit of code on your page(s), and you'll have an ad bar just like the one you see to the right of this page.  You get paid based on a percentage of clicks through your ad links.

SendMoreInfo.com
Earn money just by reading email advertising!  We already get lots of junk email, so why not get paid for looking at some of it?  I have been using this program for over a year now, and am quite happy with it.  I get emails from them every day, and they pay out when you've earned a minimum of $10.  Trust me, it doesn't take very long to earn $10!

Hits4Pay.com
Another way to earn money by reading emails.  This one doesn't send as many emails as some of the other programs, but you get paid more for each one.  They pay out when you've earned $25, AND they'll put $10 in your account just for signing up now!!

SnapDollars
Lots of ways to earn money -- reading emails, playing games, taking surveys, signing up for free trials!  Pays the most per email of any pay-to-read service I've seen so far.

InboxDollars
One more way to earn money reading email, taking surveys, and signing up for mailing lists and free trials.  A $5 bonus to you for signing up!

Care2.com
OK, so this one won't earn you any money -- but it will earn you a hearty, heartfelt thanks from me and all the animals and habitats you'll be saving.  All it takes is one click a day!  The link above will start you on the Pets In Need page, but be sure to join and click all the other causes.  Thanks!!!