One of the quaintest relics of the analog age is the idea that a signature is worth more than the paper it's on. It's notforgers have been taking advantage of dupes well before John Hancock signed the Declaration of Independence. Nonetheless, a major tenet of business is that any agreement requires a signature. Which generally means that any time you get an emailed contract, you have to print it out, sign it, and then either rescan it or (horrors!) fax it back. (That is, if they don't make you print it out and snail mail it.)
What a waste of time. The best way we should be tackling this problem is through the use of digital signaturescomplicated and personalized bits of code that would be somewhat akin to our pin numbers. But because the US government has yet to decide the exact legal status of such "signatures," and because many of the companies you deal with are strongly governed by inertia, it's unlikely that you'll use them quite as often as your actual handwriting.
But you can still cut out a few steps by simply scanning in your signature to attach to whatever document needs it. Scan it in as "black and white" and then save it as a Bitmap file. Then, insert it into any document just as you would any picture file. None of it is particularly secure or encrypted, but then again, your signature never was.