Here are a couple of lists for
RSS Feeds Sponsors and
Morphing Feeds Sponsors - I usually go into a bit of detail about the feeds in the program reviews/overviews (via thumbs on left), especially if there is something important affiliates should be aware of upfront such as if the program no longer updates or the feeds only offer a single line of text.
As mentioned above,
AEBN is a good one especially for embedded clips - though some niches update considerably more often than others.
PimpRoll also has some good feeds, but do not work well with many feed aggregators as the guid changes daily so you'll likely end up with daily duplicate posts. Additionally, a lot of their feeds point to the sites which contain canonical links rather than galleries which would be preferable.
I also like the feeds of
21SexturyCash for consistent updates and good text descriptions, though I recently noticed some past entries linking to expired domains when pulling all updates in a single feed.
Edit: You might also be interested in looking over this list of
hosted blogs sponsors as the various programs hosted blogs generally update fairly regularly and often have extensive text.