In the last few days i wrote a android app but i won't put it in the market yet. This has different reasons; first i don't think a lot of people will use it and second i am (not yet) willing to set up a developer account and pay fees and the for me most valuable reason i don't think the app is ready to be distributed. For that reason i searched a way to distribute the app without using the market. So that it's a kind of closed alpha test. I found to was to do so:
Use the Android SDK
Install the USB driver, then do the following settings: Settings -> Application Settings and enable Unknown Sources. Also go to Settings -> SD Card and Phone Storage -> Disable Use for USB Storage. Then all you have to do is type adb install file.apk.
Use the APK install from the Market
Copy the .apk file to the root directory of your SD Card. Then install the "Apps Installer" application (There is more than one with a similar name. They all seem to work well). The rest is straight forward. Open the app, select your apk file on your SD Card and click install.