I'm trying to adjust my Digest Periodical settings but all I get is "All tags" and "----" under the heading of "What to send (filter by tag)" and I couldn't find where the tags for my RSS feeds have been placed.
Answering my own question; Digest format works with only the web pages you've send through the bookmarklet (that you can get from here; http://sendtoreader.com/user/settings) Then I'm asking for a Digest report for all my RSS feeds :)