Is there a way to save daily summary report numbers into a table to create a daily history of a report total? I want to see things like pipeline size over time.

Using the "More... " button on a Summary report you can copy the data to another table.    I would create that table first by exporting to excel and then importing to a new table in order to ensure that the field names will match up perfectly. Then in subsequent days use the option to copy to another table.

I also suggest including a summary field of Today() so that when you import to your history field it knows which day it was for.  Or maybe the native [Date Created] is good enough, I guess.