Where to find meaty RSS feeds?

I am making a feed reader that (i) would like to show you a significant amount of text in the feed and (ii) builds models to cluster and classify the text

In terms of length I like the abstracts of scientific papers on sites like arxiv.org.

I have more scientific papers now than I can stand, so I am looking for high volume RSS feeds of a huge paragraph or a few small paragraphs on any topics: the subject could be sports or javascript programming, product reviews, any kind of journalism or other non-fiction.

Good length is the first qualification but to feed this beast I would love feeds that get 10, 20 or 50 articles a day.

Any suggestions?