You can "save as" into an EPS format within Illustrator which can be read by many page layout software like PageMaker, InDesign, Quark...

or you can open your .ai file in Photoshop (which will convert it to "raster") and "save as" pretty much any of the formats available.

If you want to retain the vector aspect you need to do a "save as" so your original file remains an Illustrator file.

:)
retrocity