Simply upload your apk and access it with the android browser. The browser will offer you the installation...
The link should look like this: http://www.example.com/application.apk
i hear ya and i thought that is all it took except i get a 'the request is not supported' error in the android browser. i remember reading somewhere that the mime for .apk had to be defined. i'm just not sure what to mime .apk as.
forgot to mention that i run my own web servers so adjusting a mime is no problem, and since i am not a hosting firm i wouldn't be surprised if my mime mapping is not up-to-date with the current stuff