Do you ever wish you could be logged into multiple webmail accounts simultaneously? Maybe you have a couple of GMail accounts that you use for communicating with different people and you want to have them both open at the same time. Unfortunately, this isn't possible with many popular webmail clients, including Yahoo! and Hotmail. The reason is that these services use a cookie to keep track of who you are. You can only have one cookie per site so it would seem impossible to be able to log into multiple GMail sessions, right? Wrong. Enter Cookie Swap.
Cookie Swap is a plug-in for Firefox (yeah, yeah, I know, another Firefox plug-in post) that allows you to have multiple "cookie profiles." So, you could have one profile for one GMail account and another for your other GMail account. Each profile contains its own independent cookies that do not know about cookies in other profiles. It's pretty nice for quickly switching between accounts.
Caveat emptor: if you open multiple tabs or windows and change your profiles from profile 1 to profile 2, it changes in all of them. So, you need to remember to switch back to profile 1 when you go back to window or tab 1. This is extremely annoying and I hope they will fix this in future versions.