I'm sorry it took me so long to reply again to your question.
This is the easiest way I've found to find the forms you are looking for. On the Ancestry.com home page put your cursor on search, a drop down window will appear, click on census & voter lists, click on U.S. Federal Census Collection. On the right hand side of that page scroll down to where you see "More help". Under that heading click on blank census forms. There you will see a list of various forms and work sheets.
Some of the same forms are also available on Rootsweb.com. Other Genealogy sites also have forms you might like. I've often Googled "Genealogy Forms" or "Free Genealogy Forms" (or worksheets). Some sites have really nice tree forms you can fill out. I've seen some shaped like trees with branches and some spread out in circles or even fans. I know a gal who enlarged the tree-shaped one to a large poster size. And when she finished filling in the names and other info she framed it and has it on her wall.
Now, to finally answer your original question , "What is a source summary?" According to Ancestry.com a "Sourc Summary provides quick reference to information and sources you have found for a particular family."
I'm sure you've probably found the answer to your question, but I thought I'd better try to answer it anyway.
Good Luck with your searching,