Why not supply an illustrator PDF?
You have all the benefits of a PDF (IE can be used in most programs) but with the extra that it can be dropped back into Illustrator as an .AI - Supplied along with a JPEG so they can use in word.
I normally send a pack with PDFs of all types - logo, logo in white, logo in black (for faxes), symbol only, text only and jpg.
I have just started supplying an avatar version in the pack after seeing a incredibly badly optimised version of a logo I designed on a forum. I've been surprised at how amazed people get when they see I've included an avatar for them.
Also.... HI.... 1st post on this lovely forum! :icon_biggrin: