Gmail's IMAP support is one of the biggest things to hit the webmail world since, well, Gmail. We've already covered how to use imap from Outlook, and now it's time to show everybody how to use it from the open-source Mozilla Thunderbird email client.
Nowadays, many people maintain separate email accounts for work, for family and friends, to post into forums, and so on. I use several Gmail accounts, and I find it a challenge to read all those accounts without having to set up a POP client or disconnecting and connecting to the Gmail Web site with a browser over and over again. Gmail Manager is an OS-independent Firefox extension that can help anyone with that problem. With it, you can manage multiple accounts and be notified as soon as you receive a new message in any of them.