From the Library of Congress authorities.
Use for: Blogging, Blogs, Filters (Weblogs), Newspages (Weblogs)
See also: Diaries, Web sites
You should also read the 670 notes and see what you think of the sources used for defining weblogs. This authority was created back in 2003 so keep that in mind.
There’s no authority for RSS, I couldn’t find even syndication other than for television programs, nothing for aggregators, and feeds just gets you stuff on nutritional preparation for animals by humans. In our catalogue at work, any items that discuss RSS and/or syndicating web sites are indexed as “Web sites–design” or “web site development”, and sometimes they include “XML (document markup language)” or “MPLS standard” but I don’t know what multi protocol label switching is. If I had to catalogue an item on RSS, I think I’d be somewhat dissatissfied with my options for subject headings.
Just thought I’d share.