Hello. I host an unofficial RSS feed for Sinfest.
Access it at http://bin.piorkowski.ca/sinfest-rss/rss2.xml.
As the feed file contains only the most recent comic, you should use an RSS reader that updates at least daily or some comics will be missing. The feed updates nightly 23:30 U.S. Pacific time (07:30 UTC, 06:30 UTC during U.S. summer time).
Please report issues via email (listed on my homepage) or this project's Github.