there is a method to get .apk from the android market. But just a disclaimer, this doesn't apply to every app on the market.
Just click the app author's name and it will show you the list of other apps the author has on the market. On that page, there is a link saying "visit website for <author>", follow that link. If the author has his website tied directly to sites.google.com, at the bottom of that page there are options to download the .apk of his apps directly to your PC. Of course this mostly happens to apps which are free to begin with.
But just in case, you can also try going to the author's main website and check if they offer their apps as direct .apk download. HTH