How many times can I install an application I've purchased on the Market? I have just bought an HTC HD2 and I immediately installed a custom Android ROM. I will probably change ROMs often.

If I buy an application from the Android Market how many times can I download and install it?
As long as you are using the same Google account, you should be able to download it as many times as you need to.  The Android Market keeps track of who has bought which applications and allows them to be re-downloaded.