Android phones allow users to grab apps outside the official Market, but it usually involves either USB transfer or some tricky browser navigation. Lifehacker reader cinnamonster points out the smarter solution — use the Dropbox file syncing app to grab installers.
Grab the app you want from a full-fledged browser on your desktop, then drop it in Dropbox on your system. I created an Android Apps folder for the purpose, but it's not necessary. Then open up the Dropbox app on your Android phone, navigate to that .apk file you downloaded and click it there. Your phone will open up its installer, and you'll be all set to go. You'll also need to have non-Market sources enabled in your Applications settings.