Realtrix has a very good hack on making Related Posts for blogger.com / blogspot. It works well. This is the simple way how to do it (visit Realtrix post for more details):
1. After login to your blogger.com -> layout -> Edit HTML -> Expand Widget Templates
2. Find the following code
and
1. After login to your blogger.com -> layout -> Edit HTML -> Expand Widget Templates
2. Find the following code
and