The Broadsides collect recent blogging and history news noted by the History Carnival's friends on Twitter. They are curated by the History Carnival and updated about three times a week. (Broadsides RSS; email option.)
The Bulletins aggregate popular links on Twitter that have been tagged with #hashtags frequently used by tweeting historians. These collections are entirely computer generated and the feeds are checked for updates several times a day. (RSS feed for all bulletins.)
Bulletins currently active (with more to come):