This site has some great extensions that I haven’t seen before. My biggest find here was an extension that allows you to Fcc – in other words, while composing your message, you can designate that it will get saved in a particular folder (other than your default “Sent” folder) – this is great if you’re delegating a task to someone and thus want to file your email to them in a @Wait (or @Delegated) folder so that you can check your open loops periodically. There are some other great extensions at this site, like one that allows you to use shortcut keys to quickly move messages to folders of your choosing and another that lets you edit the subject and date of messages.