How can I install Skype on my Acme tablet? I have Acme 7" tablet. How can I install Skype on it? When I go to the Skype for Android site it seems to allow installation for mobiles only.

Also, when I go to the Android Market and sign in with my Google account it says that "There are no Android phones associated with this account". How do I manage my tablet from the web interface so I will be able to download apps from the Market?
If you don't want to/can't install the market on your tablet, you can download the .apk file for an app either directly from a website on your tablet or download it on your PC and then transfer it to your tablet.  After that you can use any file manager to navigate to the APK and then click on it to install it (you have to have third party app installation turned on).  

I usually get my APKs at Android Community for Devs