[Ken Case]

You'll find "Smaller" and "Bigger" in the Format menu under the Font submenu. (They have the keyboard shortcuts Command-Minus and Command-Plus.)

You might also find the "Paste and Match Style" command useful. It's in the Edit menu, and is just like Paste except that it strips the original style formatting so that your pasted text matches the surrounding text. (The only awkward thing about it is its keyboard shortcut: we're using the standard shortcut used by Mail, iChat, etc., which is Option-Shift-Command-V. You can use System Preferences to bind it to a more convenient key, though!)

Hope this helps!