If you own a number of android devices, you can now install the apps that you have one device on all the other android devices without having to purchase multiple copies of the same apps for each one of your android devices. Android Market of versions 3.0 and higher offers you the ability to do just that by letting you download all your paid apps on your other android devices and that too at no extra cost.
Go to android settings and select accounts and sync. From there go to Add Account and enter the account that you used to purchase the app that you want to install on your android device. Go to the Android Market, from the Menu choose Accounts and select the appropriate account. Now select My Apps from Menu and you will be able to see all the apps that you have purchased with that account from the Android Market.
If you scroll down you will see a section Not Installed which will show all the apps that you have not installed on the device. You can just tap on the listed apps to go to the Android Market and click Install to install it on that device.