If you are using labels like "Older" and "Newer", then I don't think it really matters much. However, I think that using "Older" and "Newer" is incorrect, and "Next Page" and "Previous Page" are better labels. The reason for this is that most people associate links displayed like this as paging links, and as such, they expect it to work like this:
<< Previous Next >>
This is the opposite of your last example.
This follows the paging mechanisms used by searches (both site-level and search engines), so the user experience is well known.
I understand that the default for most blog platforms is to use the "older/newer" paradigm, but that actually leads to confusion. I can't count the number of times when I've clicked the "newer" link and been confused on a blog by seeing the list of posts I had just looked at. Why did I get confused? The "newer" link starts with 'N' and so does "next". I (like most users, I'm sure) are so used to seeing "next" and "previous" that that link starting with 'N' automatically gets associated with the next page of results, even if that's completely wrong.
Back to the order of "newer" and "older", I actually think that for blogs, the example that confuses you:
<< Newer Posts Older Posts >>
makes more sense, because then at least the link on the right (pointing "forward") is the link to the next set of posts that you haven't already viewed.
UPDATE: Adding some additional information:
Take a look at the default for Wordpress (using their official blog as an example):
If you scroll all the way to the bottom, you will see Newer/Older displayed just as I lay out here. Now, take a look at the URL: page/3/
What URL would you expect to see when you clicked on "older posts"? page/2/ or page/4? If there's any ambiguity here, then the links are poorly named.
What would you expect to see on page/4/? Would you expect to see older or newer posts? On a blog, you expect to see older posts. Since the number is increasing, then the "Older" link definitely makes the most sense to be on the right, since that's how the paging design pattern works (Don't believe me, look at this site, google, anything you want).
Because people clearly understand that the display of a blog does not follow an oldest to newest pattern (although comments and answers on this page seem to contradict that), and people DEFINITELY understand the paging pattern ("forward" takes you to the next page) it makes more sense to not even display older/newer. Hence the reason that next/previous are a better option. If a user is on the above URL, and they click Next, they definitely would expect to see page/4/ (already resolves the ambiguity issue). And because in general, users DO know that the front page of a blog has the newest posts, they know what they are going to be getting when they click Next from that page.