From their site: "Paterra, Inc. is pleased to provide classification-based RSS news feeds for U.S. pregrant patent publications.
This service is free. No registration is required.
These feeds are updated weekly.
RSS news feeds can be set up for each U.S. patent classification starting at the top subclass level or for each IPC class starting at the main group level. To find a news feed, expand your desired class then click on the number of the desired subclass."