Is there a way to find out if someone has blocked you from AIM?

The best way would probably be to ask a friend (or multiple friends) to put this person on their buddy list, and if they see the person online, let you know. When they do, you can see if they appear on your buddy list. If so, they have not blocked you. If their name is not there, then they have blocked you.

You can also do this yourself by creating a new screen name, adding the person to your new buddy list, and linking your two screen names (edit>settings>buddy list>linked screen names) so they are both online at once.

Note that this will only work if the person does not have settings where only his or her friends can see the screen name's online status.

You can also use > to see if they are online. This will tell you when they are online, mobile, or offline. If they are online or mobile, and you don't see them in your buddy box, then you more than likely Blocked.