The new Leopard Preview has some great features, including editing and rearranging pages in a PDF file. However, what you might not know is that you can take some number of images and create a single PDF out of those images.
To create a single PDF from multiple TIFF, JPG, or other supported file types, do this:
Open any PDF -- single or multi page, it doesn't matter -- in Preview. You'll remove it later, so any image will do.
Show the sidebar (either Shift-Command-D, or via the menu or toolbar button).
Drag the single page images you want to use to the sidebar. They will be formated one per page.
Select the PDF you opened in step one -- use Shift-Click to select multiple pages, then choose Edit » Delete. Don't worry, this image is not actually erased from your hard drive, just 'deleted' from the sidebar.
Selected File » Save As »...