[rickr]

You shouldn't need a yagi to listen to ham sats (transmit you will). A good external omnidirectional antenna should be fine.

In addition to the sats ISS always has at least one ham radio operator. They sometimes man the radio and make contacts with hams. In addition to THAT sometimes they operate SSTV (sending pictures via radio) that you would be able to pick up. Very cool stuff!

Here's a good site to see where hamsats are: http://www.amsat.org/