Uncomplex has released Mailplane 3.0.1, a maintenance release to the Gmail-specific mail client that revises keyboard shortcuts for opening mail due to a change that enables shortcuts to work in reply mode. The previous Mail > Open option has been revised to Mail > Open Conversation (Command-]), while Mail > Open In New Window has been added (Command-O). The update also lets you hide the tab bar, fixes an AppleScript issue with paragraphs in the mail body, squashes a bug with downloaded attachments containing special characters in their file names, and ensures that opening a file dialog no longer crashes the app in Mac OS X 10.7 Lion. ($24.95 new, free update, 20-percent-off upgrade discount or free upgrades for purchases after 1 October 2012, 3.6 MB, release notes)
Adding Links in Snow Leopard's Mail
Apple Mail in Snow Leopard now has a Command-key shortcut for adding a link to an email.
If you use plain-text email, this will not be helpful at all, but if you send styled email, it's a nice shortcut for adding URLs to your email messages. Simply select the word(s) you want to make into a link, press Command-K, and enter the URL to build into the link.