I love and hate cookies. I love the fact that I can go to certain
"safe" sites and they'll remember certain settings. Google, PageFlakes, Blogger, etc. would be good examples of this.
Then there's the other guys... I don't want everyone and their mother knowing what I browse, or when. To increase my privacy I like to disable 3rd Party cookies, but the DEVs removed the simple click-box to do this in later version of Firefox.
Here's how to add it back:
1. Type in about:config in the address bar and hit enter
2. Edit the value for network.cookie.cookieBehavior and set it to 1.
1 = Accept cookies from this site only, 0 = accept all cookies, 2 = accept no cookies, 3 = use P3P policy
...I also modified the network.cookie.lifetime.days value so that the cookies expire much sooner.
Check out this MozillaZine page for more great info.