You have a few options. One of the easiest is to open a new word processing document, move to Mail, select the text that you’d like to copy in an email message and drag the text to the open word processing document.
If you’d like to automate the process – as well as easily add text snippets to a single document – Snow Leopard’s Automator can do that. You’d create a Mail-to-Pages workflow this way:
Launch Automator and, in the Template sheet that appears, select Service and click Choose. In the window that appears, add these actions: Copy To Clipboard and Launch Application. Configure the top of the window to read Service Receives Selected Text In Mail. In the Launch Application action, choose Pages from the pop-up menu. (If you don’t see a Pages listing, choose Other at the bottom of the menu and navigate to the Pages application, which is likely in the iWork ’09 folder in your Applications folder.)
Launch Pages and open a new blank document. Return to Automator and click the Record button. An Automator Record window will appear, complete with a Stop Recording button. Return to Pages and press the Return key twice. Click the Stop Recording button. A Watch Me Do action will appear in your Automator workflow. Delete everything in the action except the Type command.
Click Automator’s Record button again, switch to Pages and press Cmd-V. Click the Stop Recording button and return to your Automator workflow. In the new Watch Me Do action, delete everything except Press Cmd-V. In the Timeout area of this action, enter 5 seconds. Save your workflow and enter a name for it when prompted.
What did we do? The first action asks Automator to copy the selected text in the email message. The second action switches to Pages. (Even though the action is called Launch Application, it will switch to an application if that application is already open.) The third action inserts two blank lines – necessary when you want to easily separate one bit of pasted text from the next bit. And the last action pastes the text from the Clipboard into the Pages document (Automator doesn’t include a Paste Text action of its own, which is why we had to use Watch Me Do).
This workflow becomes more effective when you launch System Preferences, select the Keyboard preference, click Keyboard Shortcuts, choose Services, locate the service you just created (it will appear under the Text heading), click to the right of the service and assign a keyboard shortcut to it. This makes the service easier to invoke later. You can also choose it from Mail’s Services menu if you want.