I am having to merge a number of seperate sites into one site. I plan to use 301's on their old urls, to point to a subfolder, and not the index page of the main site. i.e. www.blue-widgets.com is now going to have a 301 pointing to www.widgets.com/blue.
I wonder if google will transfer the PR through to that subfolder. And also whether it will think this is spam or not.
AFAIK it will not hurt you. You are telling googlebot that those links are no longer there and have moved permanently to that subfolder. I believe this is the way Google wants you to do it. I am not sure if there will be any PR benefit.