How to block a phone number in Android?

Occasionally, there is some situation that you do not want to answer calls from a particular person. So, many cellphones provide "blacklist" function -- you put a phone number into this blacklist, and your phone will ignore calls from this number.

It seems that my Android phone does not directly support this function. But, you can get pretty much the same result by using the following trick: open your phonebook, edit the contact you want to block, choose "Send calls directly to voicemail", done!

I heard the latest Android (Android 2.2?) has the blacklist function. It will be a useful function to many users.