This whole 'electronic mail' really seems to have taken off with the internets, and we need to rely on it for an increasing amount of communication with email lists, coworkers, friends and more. While many Mail.app users have at least some sort of Rules system for filing messages into folders (or tagging them with Scott Morrison's spectacular MailTags plugin), I have recently been getting cozy with a lesser-known feature that can save a lot of time with hopping between folders. Under Mail.app's File menu is a New Viewer Window option (opt-cmd-n) that opens - drum roll please - a second window in which you can browse through your messages. This is particularly useful if you have a folder (or perhaps a Smart Folder) which you keep checking throughout the day; this way, you can simply keep one viewer open to your inbox (or whatever default location that suits you), with the second viewer set on that other folder. Go up to View > Hide Mailboxes (cmd-shift-m) for either window to give you some extra room to stretch out those From or Subject headings, and you just took another step up the ladder of email zen. Finally: have no fear if you need to quit Mail or restart - Mail remembers your multi-viewer setup and will put everything right back where it belongs the next time your get your email on.