The posts are categorized by product, so that if I want to see posts on Backpack, I can do so. Posts spanning multiple products are assigned to multiple categories; an example of such a post is the one on Basecode, the Firefox extension that allows formatting of text inside 37s applications.
I don’t think that there is a separate RSS feed for each product. So I have to subscribe to the whole product blog, rather than being able to subscribe to the posts on Basecamp. Had 37s gone with WordPress, it would have been easy to provide a feed for each product.
The product blog seems to be running on TypePad. 37s’ Signal vs. Noise blog is, as far as I know, still running on Blog Cabin, which 37s developed but does not sell. I’ll ask about the choice of tool for the product blog in what I think is the appropriate place.
Update: in that appropriate place, and in a comment to this post, 37s points out that TypePad would allow a feed for each product, but that the product blog doesn’t currently use that feature of TypePad.