Out of curiosity, I was checking out some Firefox Add-ons and founds something called GrabMyBooks. GrabMyBooks lets you grab RSS feeds, web pages, bits of text on websites, and possibly other things I haven't learned about yet. Once you've grabbed what you want to read, it converts the whole thing into an EPUB file, which you can then read on your e-reader.
I've only tried it out a little so far, but it's pretty simple to use. I tried adding a couple feeds to it - it only works well if the feed is set to give you the full contents of posts, which isn't really surprising, but means that I can't just add Dear Author's feed. What I can do for a blog like Dear Author, however, is right-click on posts I'd like to read, choose "Grab this page," and GrabMyBooks will add the post to the list of things I want converted into an EPUB file.
From what I can tell, this add-on will only grab text, so if you're hoping to read something image-heavy on your reader using this tool, you're out of luck. Also, sometimes the grabs look a bit wonky. I tried adding the RSS feed for my own blog, and it couldn't seem to handle my bulleted lists of read-alikes and watch-alikes. Fortunately, GrabMyBooks has an easy-to-use editing feature that will let you go into each article and correct any formatting issues before you convert the whole thing into an EPUB file. It will also let you reposition the order that the articles are in, although you'll have to do this one by one.
I've only briefly looked at the results in my Nook. It looks like there might be some text-wrapping issues, but the results are still readable.
While I would still love it if the Nook's The Daily feature were a built-in RSS feed reader that allowed you to read whatever RSS feeds you wanted, online or offline (after getting online to refresh the feed), this seems like a good potential workaround.
------------------------UPDATE, 6/11/11 - I did a bit more playing around with this add-on and the EPUB files it produces. No, it's not perfect. I would love if it had an option that allowed for the inclusion of images. I would love it if the title of the blog entry, article, web page, etc. were grabbed along with the body text - instead, you get the URL of the page. If you leave that URL as is and it's really long, it might not display in its entirety, or at least that's what happens on my Nook. Fortunately, you can change this bit of text using the add-on's edit feature. I would prefer it if the title were just automatically included, however.
I was wrong about a couple things. First, you can grab entries from RSS feeds that are set up to only display partial articles (up to the jump break). Second, that text-wrap issue turned out to only be a problem on one blog post. I'm not sure why that blog post had problems when none of the others did.
Another thing I like about this add-on - each "article" (blog post, grabbed web page text, etc.) is treated like a chapter, so, on the Nook, I can jump to a particular article (the default chapter title for each post/article/bit of grabbed text is "Article #", where # is a number, but I think you might be able to change this in the add-on's edit mode - I haven't tried this yet).
Some things I wish this add-on could do: I grabbed a couple blog posts, but didn't turn them into an EPUB file. I turned off my computer. When I turned my computer back on, there were no grabbed posts. It would be nice if there were a way to save your grabbed posts so you could accumulate however many you like and then create an EPUB file when you've decided you have enough things collected. I would also like it if there were a way to mark RSS feed entries as having been added to an EPUB file. At first, it looked like the ones that hadn't been added stayed bolded, while the ones that had were no longer bold. However, when I turned off my computer and then later got back on, all entries were bolded again.
For the most part, this seems to be a really nifty and useful Firefox add-on. Now I've got a whole bunch of posts I'd been meaning to catch up on saved on my Nook, for reading during spare moments here and there.